Heating plate, conductive pattern sheet, vehicle, and method of manufacturing heating plate

ABSTRACT

A heating plate  10  includes: a pair of glass plates  11, 12 ; a conductive pattern  40, 70  disposed between the pair of glass plates  11, 12  and defining a plurality of opening areas  43, 73 ; and a joint layer  13, 14  disposed between the conductive pattern  40, 70  and at least one of the pair of glass plates  11, 12 ; wherein the conductive pattern  40, 70  includes a plurality of connection elements  44, 74  that extend between two branch points  42, 72  to define the opening areas  43, 73 ; and a rate of the connection elements  44, 74 , which are straight line segments connecting the two branch points  42, 72 , relative to the plurality of connection elements  44, 74 , is less than 20%.

TECHNICAL FIELD

The present invention relates to a heating plate, a conductive patternsheet for the heating plate, a vehicle having the heating plate, and amethod of manufacturing the heating plate.

BACKGROUND ART

As a defroster apparatus used for a pane, such as a front window and arear window of a vehicle, a defroster apparatus locating a heating wireformed of a tungsten wire or the like all over the pane is known. In theconventional technique, by powering the heating wire provided all overthe pane to raise a temperature of the pane by means of resistance heat,the pane is defogged or defrosted to ensure a field of view of apassenger.

In a defroster apparatus disclosed in JP2013-173402A, a tungsten wire isused as the heating wire. In this case, the heating wire has anincreased cross-sectional area in order to prevent that electricresistance of the heating wire becomes too high because of a higherelectric resistivity of tungsten. Thus, the heating wire using thetungsten wire is easily visible to an observer. The fact that theheating wire is visible to an observer such as a driver deteriorates avisibility of the observer through the pane.

There is recently known another defroster apparatus manufactured bycreating a conductive pattern by photolithographic technique in place ofa heating wire formed of a tungsten wire or the like. By powering theconductive pattern, a temperature of a pane is raised by means ofresistance heat (JP2011-216378A and JP2012-151116A). This method isadvantageous in that even a conductive pattern of a complicated shapecan be easily formed. In JP2011-216378A and JP2012-151116A, a conductivepattern having an irregular shape obtained from a Voronoi diagram isformed, and the conductive pattern is used as a heating wire for raisinga temperature of a pane.

FIG. 23 shows a partially enlarged conductive pattern 540 of aconventional defroster apparatus disclosed in JP2011-216378A andJP2012-151116A. In the conventional defroster apparatus, the conductivepattern 540 includes a plurality of connection elements 544 that extendbetween two branch points 542 to define opening areas 543. Eachconnection element 544 is formed of one straight line. The inventors ofthe present invention have conducted extensive studies on the defrosterapparatus having such a connection element 544 and found that theconductive pattern 540 including the connection elements 544 may bevisible to an observer (e.g., a passenger such as a driver), because ofthe shape of each connection element 544 formed of one straight line.When light such as outside light incident on the defroster apparatusenters a side surface formed of a flat surface of the connection element544, the light incident on each position of the side surface isreflected on the side surface in substantially a certain direction. Thereflected light is visible to an observer so that the conductive pattern540 including the connection elements 544 is visible to the observer.The fact that the conductive pattern 540 including the connectionelements 544 is visible to the observer such as a driver deteriorates avisibility of the observer through the pane.

The present invention has been made in view of the above circumstances.The first object of the present invention is to improve an invisibilityof the conductive pattern of the defroster apparatus.

Various materials have been conventionally used for a heating wire ofthe defroster apparatus. For example, JP9-207718A discloses that aheating wire is made of tungsten. The heating wires disclosed inJP9-207718A are arranged in a so-called line and space pattern in whichthe plurality of heating wires are arranged in one direction.

The heating wire (thin conductive wire) in the defroster apparatus isdesired to be as thin as possible, in order to improve a see-throughproperty of a pane. However, the heating wire made of tungsten as inJP9-207718A has a relatively higher volume resistivity. Thus, inconsideration of heat generation by the resistance heat of the electricwire upon being powered, it is difficult to make extremely thinner theheating wire. Thus, when the heating wire as disclosed in JP9-207718A isused in the defroster apparatus, there is a difficulty in exhibiting anexcellent see-through property, while realizing a suitable heatgeneration function.

When the heating wires made of tungsten as disclosed in JP9-207718A areused in the defroster apparatus, the heating wires are sometimesheated/pressurized while being sandwiched between a pair of glassplates. In this case, before the heating/pressurizing step, the heatingwires are generally manufactured as thin wires in a separate step. Theheating wires formed in the separate step are placed and positioned in adesired pattern between a pair of glass plates, and the pair of glassplates in this condition are heated/pressurized. However, thispositioning operation requires time and effort in order to preciselyposition the electric wires. In addition, when the pair of glass platesare heated/pressurized, there is a possibility that the electric wiresare shifted from the determined positions.

The present invention has been made in view of the above circumstances.The second object of the present invention is to provide a heating plateand a method of manufacturing the same, which is capable of achieving anexcellent see-through property because thin conductive wires disposedbetween glass plates are sufficiently thin, and of achieving anexcellent heat generation upon being powered although the line widths ofthe thin conductive wires are thin, while a desired pattern of the thinconductive wires can be easily given to the heating plate with highprecision.

In addition, the third object of the present invention is to provide aheating plate, a pattern sheet and a method of manufacturing the same,which is capable of achieving an excellent see-through property becausethe thin conductive wires disposed between glass plates are sufficientlythin, and of achieving an excellent heat generation upon being poweredalthough the line widths of the thin conductive wires are thin.

JP2010-3667A discloses that heating wires are formed by exposing,developing and fixing a silver-salt photosensitive layer on a substrate.In addition, JP2010-3667A discloses that heating wires are formed bylaminating a metal foil on a substrate and etching the metal foil, andthat heating wires are formed by printing a paste containing metalparticles on a substrate. Further, there is disclosed that heating wireare formed by printing heating wires on a substrate by means of a screenprinting plate.

In such a defroster apparatus, a pair of glass plates, with a jointlayer and heating wires being sandwiched therebetween, are heated andpressurized so as to manufacture a heating plate, and a defrosterapparatus is formed of the heating plate. When such a heating plate ismanufactured with the use of the heating wires disclosed inJP2010-3667A, the heating wires, which are integral with a sheet-likesubstrate, are disposed between a pair of glass plates, and then heatedand pressurized. In more detail, a glass plate, a joint layer, asubstrate integral with the heating wires, a joint layer and a glassplate are superposed in this order, and then heated and pressurized. Inthe thus manufactured heating plate, the one joint layer of the twojoint layers is directly in contact with the glass plate and thesubstrate to join the glass plate and the substrate, and the other jointlayer is directly in contact with the heating wire and the glass plateto join the heating wire and the glass plate.

Each heating wire disclosed in JP2010-3667A is formed to project along anormal direction of a sheet plane of a sheet-like substrate, and asidewall thereof extends along the normal direction of the sheet pale ofthe substrate. The sidewall of such a heating wire may have an overhangshape, for some reason or other in the course of manufacture. Theoverhang shape means a shape of a heating wire that sidewall of theheating wire inclinedly extends to the outside in a direction along thesheet plane of the substrate, as a certain point in the sidewall movesaway from the substrate along the normal direction of the sheet plane ofthe substrate. Such an overhang shape particularly tends to be formedwhen a heating wire is formed by etching or by printing a pastecontaining metal particles.

However, in the case where the sidewall of a heating wire has a shapethat extends along the normal direction of the sheet plane of thesubstrate or the overhang shape, when the heating wire and the jointlayer are brought into contact with each other in the heating andpressurizing step during the manufacture of a heating plate, it isdifficult for the joint layer to get into a root side of the heatingwire, so that bubbles are likely to remain around the sidewall of theheating wire. These bubbles may impair an appearance quality of theheating plate as well as resulting in glaring (glittering). Thus, in themanufacture of the heating plate, countermeasure against remaining ofthe bubbles is desired.

The present invention has been made in view of the above circumstances.The fourth object of the present invention is to restrain remaining ofbubbles in a heating plate.

DISCLOSURE OF THE INVENTION

A first object of the present invention is to improve invisibility of aconductive pattern in a defroster apparatus. The first object isachieved by a first embodiment of the present invention.

A heating plate according to the first embodiment of the presentinvention includes:

a pair of glass plates;

a conductive pattern disposed between the pair of glass plates anddefining a plurality of opening areas; and

a joint layer disposed between the conductive pattern and at least oneof the pair of glass plates;

wherein:

the conductive pattern includes a plurality of connection elements thatextend between two branch points to define the opening areas; and

a rate of the connection elements, which are straight line segmentsconnecting the two branch points, relative to the plurality ofconnection elements, is less than 20%.

In the heating plate according to the first embodiment of the presentinvention, the conductive pattern may be formed by patterning aconductive layer by etching.

In the heating plate according to the first embodiment of the presentinvention, an average distance between centers of gravity of the twoadjacent opening areas may be not less than 80 μm. The average distancebetween centers of gravity of the two adjacent opening areas may be notless than 70 μm.

In the heating plate according to the first embodiment of the presentinvention, a thickness of the conductive pattern may be not less than 5μm. A thickness of the conductive pattern may be not less than 2 μm.

In the heating plate according to the first embodiment of the presentinvention, an average of ratio (L₁/L₂) of a length L₁ of each openingarea along a first direction, relative to a length L₂ of the openingarea along a second direction perpendicular to the first direction, maybe not less than 1.3 and not more than 1.8.

A conductive pattern sheet according to the first embodiment of thepresent invention includes:

a substrate; and

a conductive pattern disposed on the substrate and defining a pluralityof opening areas;

wherein:

the conductive pattern includes a plurality of connection elements thatextend between two branch points to define the opening areas; and

a rate of the connection elements, which are straight line segmentsconnecting the two branch points, relative to the plurality ofconnection elements, is less than 20%.

A vehicle according to the first embodiment of the present inventionincludes the aforementioned heating plate.

According to the first embodiment of the present invention, it ispossible to improve invisibility of a conductive pattern in a defrosterapparatus.

The first object of the present invention is achieved by a secondembodiment of the present invention.

A heating plate according to the second embodiment of the presentinvention includes:

a pair of glass plates;

a conductive pattern disposed between the pair of glass plates andincluding a thin conductive wire; and

a joint layer disposed between the conductive pattern and at least oneof the pair of glass plates;

wherein:

the thin conductive wire of the conductive pattern has a first surfacefacing one of the pair of glass plates, and a second surface facing theother of the pair of glass plate; and

when a width of the first surface of the thin conductive wire isrepresented as W_(2a) (μm) a width of the second surface of the thinconductive wire is represented as W_(2b) (μm), and a cross-sectionalarea of the thin conductive wire is represented as S_(2a) (μm²), thefollowing relationships represented (a) and (b) are satisfied.

0<IW _(2a) −W _(2b) I≦10  (a)

S _(2a)≧10  (b)

In the heating plate according to the second embodiment of the presentinvention, the conductive pattern may be formed by patterning aconductive layer by etching.

In the heating plate according to the second embodiment of the presentinvention, the conductive pattern may includes a pattern defining aplurality of opening areas; and the conductive pattern may include aplurality of connection elements that extend between two branch pointsto define the opening areas.

In the heating plate according to the second embodiment of the presentinvention, an average of the number of the connection elements extendingfrom one branch point may be more than 3.0 and less than 4.0.

In the heating plate according to the second embodiment of the presentinvention, the conductive pattern may include opening areas surroundedby four, five, six and seven connection elements, respectively; andamong the opening areas included in the conductive pattern, the numberof opening areas surrounded by six connection elements may bepredominant.

In the heating plate according to the second embodiment of the presentinvention, at least some of the plurality of connection elements mayhave a curved shape or a polygonal line shape, when viewed in a normaldirection of a plate plane of the heating plate.

A conductive pattern sheet according to the second embodiment of thepresent invention includes:

a substrate; and

a conductive pattern disposed on the substrate and including a thinconductive wire;

wherein:

the thin conductive wire of the conductive pattern has a proximalsurface forming a surface on the side of the substrate, and a distalsurface facing the proximal surface;

when a width of the distal surface of the thin conductive wire isrepresented as W_(2c) (μm), a width W_(2d) of the proximal surface ofthe thin conductive wire is represented as W_(2d) (μm), and across-sectional area of the thin conductive wire is represented asS_(2b) (μm²), the following relationships represented (c) and (d) aresatisfied.

0<IW _(2c) −W _(2d) I≦10  (c)

S _(2b)≧10  (d)

A vehicle according to the second embodiment of the present inventionincludes the aforementioned heating plate.

According to the second embodiment of the present invention,invisibility of a conductive pattern in a defroster apparatus can beimproved.

A second object of the present invention is to provide a heating platecapable of obtaining an excellent see-though property because a thinconductive wire disposed between glass plates is sufficiently thin,capable of obtaining suitable heat generation upon being poweredalthough a line width of the thin conductive wire is thin, and to whichthin conductive wires in a desired pattern can be easily givenprecisely, and a manufacturing method thereof. The second object isachieved by a third embodiment of the present invention.

A first heating plate according to the third embodiment of the presentinvention includes:

a pair of glass plates; and

a conductive pattern disposed between the pair of glass plates;

wherein:

the conductive pattern includes a plurality of thin conductive wiresthat are formed of a patterned copper film and are arranged in onedirection, each thin conductive wire extending in the other directionnot in parallel with the one direction apart from another thinconductive wire adjacent in the one direction;

a line width of the thin conductive wire is not less than 1 μm and notmore than 20 μm; and

a pitch between the adjacent thin conductive wires is not less than 0.3mm and not more than 2 mm.

A second heating plate according to the third embodiment of the presentinvention includes:

a pair of glass plates; and

a conductive pattern disposed between the pair of glass plates;

wherein:

the conductive pattern includes a plurality of thin conductive wiresthat are formed of a patterned copper film and are arranged in a lineand space pattern;

a line width of the thin conductive wire is not less than 1 μm and notmore than 20 μm; and

a pitch between the adjacent thin conductive wires is not less than 0.3mm and not more than 2 mm.

In the first or second heating plate according to the third embodimentof the present invention, each thin conductive wire may extend in apattern of a polygonal line shape or in a pattern of a corrugated shape.

In the first or second heating plate according to the third embodimentof the present invention, the copper film may be an electrolytic copperfoil. In this case, a thickness of the electrolytic copper foil may benot more than 7 μm.

A manufacturing method of the first heating plate according to the thirdembodiment of the present invention is a manufacturing method of aheating plate including a pair of glass plates and a conductive patterndisposed between the pair of glass plates, the manufacturing methodincluding:

laminating a copper film on a substrate; and

forming the conductive pattern including a plurality of thin conductivewires formed by patterning the copper film;

wherein:

the plurality of thin conductive wires are arranged in one direction;

each thin conductive wire extends in the other direction not in parallelwith the one direction apart from another thin conductive wire adjacentin the one direction; and

a line width of the thin conductive wire is not less than 1 μm and notmore than 20 μm, and a pitch between the adjacent thin conductive wiresis not less than 0.3 mm and not more than 2 mm.

A manufacturing method of the second heating plate according to thethird embodiment of the present invention is:

a manufacturing method of a heating plate including a pair of glassplates and a conductive pattern disposed between the pair of glassplates, the manufacturing method including:

laminating a copper film on the substrate; and

forming the conductive pattern including a plurality of thin conductivewires formed by patterning the copper film;

wherein:

the plurality of thin conductive wires are arranged in a line and spacepattern; and

a line width of the thin conductive wire is not less than 1 μm and notmore than 20 μm, and a pitch between the adjacent thin conductive wiresis not less than 0.3 mm and not more than 2 mm.

In the first or second heating plate according to the third embodimentof the present invention, the copper film may be an electrolytic copperfoil. In this case, a thickness of the electrolytic copper foil may benot more than 7 μm.

According to the third embodiment, it is possible to provide a heatingplate capable of obtaining an excellent see-though property because athin conductive wire disposed between glass plates is sufficiently thin,capable of obtaining suitable heat generation upon being poweredalthough a line width of the thin conductive wire is thin, and to whichthin conductive wires in a desired pattern can be easily givenprecisely, and a manufacturing method thereof.

A third object of the present invention is to provide a heating plateand a pattern sheet capable of obtaining an excellent see-thoughproperty because a thin conductive wire disposed between glass plates issufficiently thin, and capable of obtaining suitable heat generationupon being powered although a line width of the thin conductive wire isthin, and a manufacturing method thereof. The third object is achievedby a fourth embodiment of the present invention.

A heating plate according to the fourth embodiment of the presentinvention includes:

a pair of glass plates; and

a conductive pattern disposed between the pair of glass plates;

wherein:

the conductive pattern includes thin conductive wires formed of apatterned copper film and arranged in a mesh pattern; and

a line width of the thin conductive wire is not less than 1 μm and notmore than 20 μm.

In the heating plate according to the fourth embodiment of the presentinvention, the thin conductive wires may be arranged in a honeycombpattern.

In this case, a pitch of adjacent hexagonal openings in the honeycombpattern may be not less than 0.3 mm and not more than 7.0 mm.

In the heating plate according to the fourth embodiment of the presentinvention, the thin conductive wires may be arranged in a grid pattern.

In this case, a pitch of adjacent rectangular openings in the gridpattern may be not less than 0.3 mm and not more than 7.0 mm.

A conductive pattern sheet according to the fourth embodiment of thepresent invention is a conductive pattern sheet used in a heating platethat generates heat upon application of voltage thereto, the conductivepattern sheet including:

a substrate; and

a conductive pattern disposed on the substrate;

wherein:

the conductive pattern includes thin conductive wires formed of apatterned copper film and arranged in a mesh pattern; and

a line width of the thin conductive wire is not less than 1 μm and notmore than 20 μm.

A manufacturing method of a heating plate according to the fourthembodiment of the present invention is a manufacturing method of aheating plate including a pair of glass plates and a conductive patterndisposed between the pair of glass plates, the manufacturing methodincluding:

laminating a copper film on a substrate; and

forming the conductive pattern including thin conductive wires formed bypatterning copper film;

wherein:

the thin conductive wires are arranged in a mesh pattern; and

a line width of the thin conductive wire is not less than 1 μm and notmore than 20 μm.

According to the fourth embodiment, it is possible to provide a heatingplate and a pattern sheet capable of obtaining an excellent see-thoughproperty because a thin conductive wire disposed between glass plates issufficiently thin, and capable of obtaining suitable heat generationupon being powered although a line width of the thin conductive wire isthin, and a manufacturing method thereof.

A fourth object of the present invention is to restrain bubbles fromremaining in a heating plate. The fourth object is achieved by a fifthembodiment of the present invention.

A heating plate according to the fifth embodiment of the presentinvention includes: a heating plate including a pair of glass plates anda conductive pattern disposed between the pair of glass plates, theconductive pattern including thin conductive wires arranged in apattern, the heating plate comprising:

a joint layer disposed between at least one of the pair of glass platesand the conductive pattern, the joint layer being directly in contactwith the glass plate and the thin conductive wires so as to join theconductive pattern to the glass plate;

wherein the thin conductive wire is formed such that a line widththereof narrows as a certain point in the thin conductive wire comesclose to the glass plates located on the side of the joint layer incontact with the thin conductive wires.

In the heating plate according to the fifth embodiment of the presentinvention, the thin conductive wires may be formed from a metal filmthat is patterned by etching.

In the heating plate according to the fifth embodiment of the presentinvention, the thin conductive wire may be formed to have a trapezoidalsectional shape in a direction perpendicular to an extension directionof the thin conductive wire.

In the heating plate according to the fifth embodiment of the presentinvention, the trapezoidal sectional shape in the thin conductive wiremay have an angle which is defined by a line segment extending from anend of a lower base to an end of an upper base, with respect to adirection extending along the lower base, the angle being not less than40 degrees and not more than 85 degrees.

In the heating plate according to the fifth embodiment of the presentinvention, the thin conductive wire may have a dark color layer at aposition facing a side opposed to the glass plate located on the side ofthe joint layer in contact with the thin conductive wire. In this case,the dark color layer may be made of chrome oxide.

A conductive pattern sheet according to the fifth embodiment of thepresent is: a conductive pattern sheet having a conductive pattern to bedisposed between a pair of glass plates, comprising:

a sheet-like substrate including a pair of opposed surfaces; wherein:

the conductive pattern is provided at least any of the pair of opposedsurfaces of the substrate;

the conductive pattern includes thin conductive wires arranged in apattern; and

the thin conductive wire is formed such that a line width thereofnarrows as a certain point in the thin conductive wire moves awayoutward from the substrate along a normal direction to a sheet plane ofthe substrate.

According to the fifth embodiment of the present invention, it ispossible to restrain bubbles from remaining in a heating plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view for explaining a first embodiment accordingto the present invention, schematically showing a vehicle including aheating plate. In particular, FIG. 1 schematically shows, as an exampleof the vehicle, an automobile including the heating plate.

FIG. 2 is a view of the heating plate when viewed in a normal directionof a plate plane thereof.

FIG. 3 is a cross-sectional view of the heating plate of FIG. 2.

FIG. 4 is a plan view showing an example of a shape of a referencepattern which is referred to for determining a conductive pattern of theheating plate.

FIG. 5 is an enlarged view showing a part of the conductive patterntogether with the reference pattern shown in FIG. 4.

FIG. 6 is a view for explaining an operation of the conductive patternin the first embodiment.

FIG. 7 is a view for explaining an example of a manufacturing method ofthe heating plate.

FIG. 8 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 9 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 10 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 11 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 12 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 13 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 14 is a view for explaining a modification example of themanufacturing method of the heating plate.

FIG. 15 is a view for explaining the modification example of themanufacturing method of the heating plate.

FIG. 16 is a view for explaining the modification example of themanufacturing method of the heating plate.

FIG. 17 is a view for explaining the modification example of themanufacturing method of the heating plate.

FIG. 18 is a view for explaining the modification example of themanufacturing method of the heating plate.

FIG. 19 is a view for explaining another modification example of themanufacturing method of the heating plate.

FIG. 20 is a view for explaining the other modification example of themanufacturing method of the heating plate.

FIG. 21 is a plan view showing a modification example of the referencepattern.

FIG. 22 is an enlarged view showing a part of the conductive patterntogether with the reference pattern shown in FIG. 21.

FIG. 23 is a view for explaining a conventional technique.

FIG. 24 is a view for explaining a second embodiment according to thepresent invention, showing the heating plate when viewed in a normaldirection of a plate plane thereof.

FIG. 25 is a cross-sectional view of the heating plate of FIG. 2.

FIG. 26 is a plan view showing an example of a pattern shape of theconductive pattern of the heating plate.

FIG. 27 is a plan view showing another example of the pattern shape ofthe conductive pattern of the heating plate.

FIG. 28 is an enlarged view showing a part of the conductive pattern ofFIG. 27.

FIG. 29 is a sectional view showing a sectional shape of a thinconductive wire of the conductive pattern.

FIG. 30 is a view for explaining an example of a manufacturing method ofthe heating plate.

FIG. 31 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 32 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 33 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 34 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 35 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 36 is a view for explaining a modification example of themanufacturing method of the heating plate.

FIG. 37 is a view for explaining the modification example of themanufacturing method of the heating plate.

FIG. 38 is a view for explaining the modification example of themanufacturing method of the heating plate.

FIG. 39 is a view for explaining the modification example of themanufacturing method of the heating plate.

FIG. 40 is a view for explaining the modification example of themanufacturing method of the heating plate.

FIG. 41 is a view for explaining another modification example of themanufacturing method of the heating plate.

FIG. 42 is a view for explaining the another modification example of themanufacturing method of the heating plate.

FIG. 43 is a view for explaining a third embodiment according to thepresent invention, showing the heating plate when viewed in a normaldirection of a plate plane thereof.

FIG. 44 is a cross-sectional view of the heating plate of FIG. 43.

FIG. 45 is a view showing conditions of respective members constitutingthe heating plate of FIG. 44 before the respective members arelaminated.

FIG. 46 is a plan view showing an example of the conductive pattern.

FIG. 47 is a sectional view corresponding to an A-A line of FIG. 46,showing an example of a sectional shape of the thin conductive wire.

FIG. 48 is a sectional view corresponding to the A-A line of FIG. 46,showing another example of a sectional shape of the thin conductivewire.

FIG. 49 is a view for explaining an example of a manufacturing method ofthe heating plate.

FIG. 50 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 51 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 52 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 53 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 54 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 55 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 56 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 57 is a view for explaining a fourth embodiment according to thepresent invention, showing the heating plate when viewed in a normaldirection of a plate plane thereof.

FIG. 58 is a cross-sectional view of the heating plate of FIG. 57.

FIG. 59 is a view showing conditions of respective members constitutingthe heating plate of FIG. 58 before the respective members arelaminated.

FIG. 60 is a plan view showing an example of the conductive pattern.

FIG. 61 is a sectional view corresponding to an A-A line of FIG. 60,showing an example of a sectional shape of the thin conductive wire.

FIG. 62 is a sectional view corresponding to the A-A line of FIG. 60,showing another example of a sectional shape of the thin conductivewire.

FIG. 63 is a view for explaining an example of a manufacturing method ofthe heating plate.

FIG. 64 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 65 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 66 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 67 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 68 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 69 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 70 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 71 is a view for explaining a fifth embodiment according to thepresent invention, showing the heating plate when viewed in a normaldirection of a plate plane thereof.

FIG. 72 is a cross-sectional view of the heating plate of FIG. 71.

FIG. 73 is a view showing conditions of respective members constitutingthe heating plate of FIG. 72 before the respective members arelaminated.

FIG. 74 is a plan view showing an example of the conductive pattern.

FIG. 75 is a sectional view corresponding to an A-A line of FIG. 74,showing a sectional shape of the thin conductive wire.

FIG. 76A is an enlarged view of the sectional shape of the thinconductive wire shown in FIG. 75.

FIG. 76B is an enlarged view of the sectional shape of the thinconductive wire.

FIG. 77 is a view for explaining an example of a manufacturing method ofthe heating plate.

FIG. 78 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 79 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 80 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 81 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 82 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 83 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 84 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 85 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 86 is a view for explaining the example of the manufacturing methodof the heating plate.

FIG. 87 is a view for explaining a modification example of the heatingplate in the fifth embodiment according to the present invention.

FIG. 88 is a view for explaining another modification example of theheating plate in the fifth embodiment according to the presentinvention.

MODES FOR CARRYING OUT THE INVENTION

A plurality of embodiments of the present invention will be describedherebelow with reference to the drawings. In the drawings attached tothe specification, a scale size, an aspect ratio and so on are changedand exaggerated from the actual ones, for the convenience of easiness inillustration and understanding. In addition, structures and features ofthe embodiments described below can be suitably combined.

In this specification, the terms “plate”, “sheet” and “film” are notdifferentiated from one another, based only on the difference of terms.For example, a “conductive pattern sheet” is a concept including amember that can be referred to as plate and film, and is notdifferentiated from a member referred to as “conductive pattern plate(substrate)” or “conductive pattern film” based only on the differenceof terms.

In addition, the term “sheet plane (plate plane, film plane)” means aplane corresponding to a planar direction of a sheet-like (plate-like,film-like) member as a target that is seen as a whole in general.

In this specification, the term “joint” includes not only a “completejoint” where joint is perfectly completed but also a so-called“provisional joint” for provisional joint before the “complete joint”.

Further, in this specification, terms specifying shapes, geometricconditions and their degrees, e.g., “parallel”, “perpendicular”, “same”,etc., are not limited to their strict definitions, but construed toinclude a range with a view to obtaining the similar function.

First Embodiment

FIGS. 1 to 22 are views for explaining a first embodiment according tothe present invention. FIG. 1 is a view schematically showing anautomobile including a heating plate. FIG. 2 is a view of the heatingplate when viewed in a normal direction of a plate plane thereof. FIG. 3is a cross sectional view of the heating plate of FIG. 2. The heatingplate in this embodiment is sometimes referred to as “laminated glass”.

As shown in FIG. 1, an automobile 1 as an example of a vehicle includespanes such as a front window, a rear window and side windows. Herein, afront window 5 is formed of a heating plate 10 by way of example. Inaddition, the automobile 1 includes a power source 7 such as a battery.Heating plates 110, 210, 310 and 410 according to the other embodimentsdescribed below can be applied to the automobile of FIG. 1.

FIG. 2 shows the heating plate 10 viewed in a normal direction of aplate plane thereof. In addition, FIG. 3 shows a cross-sectional viewcorresponding to a line III-III of the heating plate 10 of FIG. 2. Inthe example shown in FIG. 3, the heating plate 10 includes a pair ofglass plates 11, 12, a conductive pattern sheet (pattern sheet) 20disposed between the pair of glass plates 11, 12, a joint layer 13(connecting layer 13) that joins (connects) the glass plate 11 and theconductive pattern sheet 20, and a joint layer 14 that joins the glassplate 12 and the conductive pattern sheet 20. In the example shown inFIGS. 1 and 2, the heating plate 10 is curved. However, FIG. 3 and FIGS.13 to 20 planarly show the heating plate 10 and the glass plates 11, 12,for simplifying the illustration and facilitating the understanding.

The conductive pattern sheet 20 includes a sheet-like substrate 30, aconductive pattern 40 formed on the substrate 30, a wiring part 15 forpowering the conductive pattern 40, and a connection part 16 connectingthe conductive pattern 40 and the wiring part 15.

In the example shown in FIGS. 2 and 3, the conductive pattern 40 ispowered by the power source 7, such as a battery, through the wiringpart 15 and the connection part 16, so that the conductive pattern 40generates heat by means of resistance heat. The heat generated by theconductive pattern 40 is transmitted to the glass plates 11, 12 throughthe joint layers 13, 14, so that the glass plates 11, 12 are warmed up.Thus, dew drops on the glass plates 11, 12 can be removed so that theglass plates 11, 12 can be defogged. When there is snow or ice on theglass plates 11, 12, the snow or ice can be unfrozen. Thus, an excellentfield of view of a passenger can be ensured.

Particularly when used as a front window of an automobile, the glassplate 11, 12 preferably has a high visible light transmittance, in ordernot to hinder a field of view of a passenger. A material of such a glassplate 11, 12 may be soda lime glass, blue plate glass (float glass) andso on, for example. The glass plate 11, 12 preferably has atransmittance of 90% or more in a visible light area. The visible lighttransmittance of the glass plate 11, 12 is specified as follows.Transmittance of light with measurement wavelength range of from 380 nmto 780 nm is measured by using a spectrophotometer (manufactured byShimadzu Corporation, “UV-3100PC”, compliant with JIS K 0115). Thevisible light transmittance is an average value of the transmittances atthe respective wavelengths. The visible light transmittance may belowered by partially or totally coloring the glass plate 11, 12, forexample. In this case, direct sunlight can be shielded and an inside ofthe automobile is less visible from outside.

In addition, the glass plate 11, 12 preferably has a thickness of notless than 1 mm and not more than 5 mm. With such a thickness, the glassplate 11, 12 excellent in strength and optical properties can beobtained.

The glass plates 11, 12 and the conductive pattern sheet 20 are joinedto each other through the joint layers 13, 14, respectively. As such ajoint layer 13, 14, a layer made of a material having various adhesionproperties or gluing (pressure sensitive adhesive) properties can beemployed. In addition, the joint layer 13, 14 preferably has a highvisible light transmittance. A typical joint layer may be a layer madeof polyvinyl butyral (PVB), for example. The joint layer 13, 14preferably has a thickness of not less than 0.15 mm and not more than0.7 mm.

Not limited to the illustrated example, the heating plate 10 may beprovided with another function layer for exerting a specific function.In addition, one function layer may exert two or more functions.Alternatively, for example, a function may be given to at least one ofthe glass plate 11, 12 of the heating plate 10, the joint layer 13, 14thereof, and the substrate 30 of the conductive pattern sheet 20thereof, which is described later. The function that can be given toheating plate 10 may be an antireflection (AR) function, a hard coat(HC) function having an an abrasion resistance, an infrared ray shield(reflection) function, an ultraviolet ray shield (reflection) function,a polarizing function, an antifouling function and so on, for example.

Next, the conductive pattern sheet 20 is described. The conductivepattern sheet 20 includes the sheet-like substrate 30, the conductivepattern 40 disposed on the substrate 30, the wiring part 15 for poweringthe conductive pattern 40, and the connection part 16 connecting theconductive pattern 40 and the wiring part 15. The conductive pattern 40is formed by arranging thin conductive wires made of metal or the likein a predetermined pattern. The conductive pattern sheet 20 may have aplanar dimension substantially the same as that of the glass plate 11,12 so as to be placed all over the heating plate 10. Alternatively, theconductive pattern sheet 20 may be placed over only a part of theheating plate 10, such as a part in front of a driver's seat.

The sheet-like substrate 30 functions as a substrate that supports theconductive pattern 40. The substrate 30 is an electrically insulatingsubstrate that transmits light of a wavelength (380 nm to 780 nm) of avisible light wavelength band, which is generally recognized astransparent.

Although any resin transmitting visible light can be used as a resin tobe contained in the substrate 30, a thermoplastic resin may bepreferably used. The thermoplastic resin may be an acryl resin made of,e.g., polymethyl methacrylate, a polyester resin made of, e.g.,polyvinyl chloride, polyethylene terephthalate or amorphous polyethyleneterephthalate (A-PET), a polyethylene resin, a polyolefin resin made of,e.g., polypropylene, a cellulose-based resin made of, e.g., triacetylcellulose (cellulose triacetate), a polystyrene or polycarbonate resin,an AS resin and so on, for example. In particular, an acryl resin and apolyvinyl chloride are preferred because of their excellent etchingresistance, weather resistance and light resistance.

In addition, in consideration of support property and light transmissionof the conductive pattern 40, the substrate 30 preferably has athickness of not less than 0.03 mm and not more than 0.3 mm.

The conductive pattern 40 is described with reference to FIGS. 4 to 6.The conductive pattern 40 is powered by the power source 7, such as abattery, through the wiring part 15 and the connection part 16, so as togenerate heat by means of resistance heat. The heat is transmitted tothe glass plates 11, 12 through the joint layers 13, 14, so that theglass plates 11, 12 are warmed up.

A first feature of the conductive pattern 40 in this embodiment is ashape typically shown in the plan view of FIG. 5. The conductive pattern40 includes a plurality of connection elements 44 that extend betweentwo branch points 42 to define a number of opening areas 43. Suchopening areas 43 have random shapes and are arranged at random pitches.Typically, the opening areas 43 have shapes which do not have a repeatedregularity (periodic regularity), and are arranged at pitches which donot have a repeated regularity (periodic regularity). A second featureof the conductive pattern 40 in this embodiment resides in that a rateof a sum of lengths of straight line segments of the connection elements44 connecting the two branch points 42, relative to a sum of lengths ofthe connection elements 44 over the whole area of the conductive pattern40, is less than 20%. Herebelow, this fact can also be expressed that “arate of the connection elements, which are straight line segmentsconnecting the two branch points, relative to the plurality ofconnection elements, is less than 20%”.

The conductive pattern 40 having the above two features is typicallyformed by determining a reference pattern 50 formed of a plurality ofling segments 54 that extend between two branch points 52 to defineopening areas 53, then determining positions of the branch points 42 ofthe conductive pattern 40 based on the branch points 52 of the referencepattern 50, and thereafter by determining positions of the connectionelements 44 of the conductive pattern 40 based on the determined branchpoints 42 of the conductive pattern 40 and the line segments 54 of thereference pattern 50.

FIG. 4 is a plan view showing the reference pattern 50. As shown in FIG.4, the reference pattern 50 is a mesh-like pattern defining a number ofthe opening areas 53. The reference pattern 50 includes a plurality ofthe line segments 54 that extend between the two branch points 52 todefine the opening areas 53. Namely, the reference pattern 50 is anaggregation of a number of the line segments 54 each forming the branchpoints 52 at both ends thereof.

In the example shown in FIG. 4, a number of the opening areas 53 of thereference pattern 50 have shapes which do not have a repeated regularity(periodic regularity) and are arranged at pitches which do not have arepeated regularity (periodic regularity). Particularly in theillustrated example, the opening areas 53 are arranged so as tocorrespond to respective Voronoi areas in a Voronoi diagram obtainedfrom generatrix points whose position coordinates in a plane have apredetermined random distribution. These randomly distributed generatrixpoints have a feature in which a distance between two adjacentgeneratrix points is distributed between a predetermined upper limitvalue and a predetermined lower limit value. In other words, therespective line segments 54 of the reference pattern 50 correspond torespective boundaries of the Voronoi areas in such a Voronoi diagram. Inaddition, the respective branch points 52 of the reference pattern 50correspond to Voronoi points in the Voronoi diagram.

Since the Voronoi diagram can be obtained by the known methods disclosedin JP2012-178556A, JP2011-216378A and JP2012-151116A, for example,detailed description of the method of creating the Voronoi diagram isomitted herein.

FIG. 5 shows, in enlargement, a part of the conductive pattern 40together with the reference pattern 50 shown in FIG. 4. Firstly, therespective branch points 42 of the conductive pattern 40 are disposed onthe respective branch points 52 of the reference pattern 50. Then, therespective connection elements 44 of the conductive pattern 40 aredisposed so as to connect the two branch points 42 corresponding to thetwo branch points 52 forming both ends of the line segments 54 of thereference pattern 50. Each connection element 44 may be formed to have alinear shape (straight line segment), a curved shape or a shape formedby combining these shapes. For example, each connection element 44 maybe formed to have a linear shape (straight line segment), an arcuateshape, a polygonal line shape, a corrugated shape and so on. A rate ofthe connection elements 44 which are straight lines (straight linesegments) connecting the two branch points 42, relative to the pluralityof connection elements 44, is less than 20%. Namely, 80% or more of theconnection elements 44 have a shape other than a linear shape (straightline segment), such as an arcuate shape, a polygonal line shape, acorrugated shape and so on.

In the example shown in FIG. 5, the conductive pattern 40 includes aplurality the branch points 42 arranged on the respective branch points52 of the reference pattern 50, and a plurality of the connectionelements 44 that extend between the two branch points 42 to define theopening areas 43. A rate of the connection elements 44, which arestraight lines (straight line segments) connecting the two branch points42, relative to the plurality of connection elements 44, is less than20%. The conductive pattern 40 has a mesh-like pattern in which theplurality of connection elements 44 are arranged correspondingly to therespective line segments 54 of the reference pattern 50.

It is not necessary to specify a rate of the connection elements 44,which are straight lines (straight line segments) connecting the twobranch points 42, relative to the plurality of connection elements 44,by checking all the area of the conductive pattern 40 and calculatingthe rate. Actually, it is possible to check the suitable number ofelements to be checked in consideration of dispersion degree ofelements, in a certain section having a planar dimension (an area) thatis considered to be capable of reflecting a general tendency of a rateof the connection elements, which are straight lines (straight linesegments) connecting the two branch points 42, relative to the pluralityof connection elements 44, and calculate the rate. A value which wasthus specified can be handled as a rate of the connection elements 44,which are straight lines (straight line segments) connecting the twobranch points 42, relative to the plurality of connection elements 44.In the conductive pattern 40 in this embodiment, by observing 100 pointsincluded in an area of 300 mm×300 mm by means of an optical microscopeor an electron microscope, a rate of the connection elements 44, whichare straight lines (straight line segments) connecting the two branchpoints 42, relative to the plurality of connection elements 44 can bespecified.

The material for constituting such a conductive pattern 40 may beselected from one or more of gold, silver, copper, platinum, aluminum,chrome, molybdenum, nickel, titanium, palladium, indium, tungsten and analloy thereof, for example.

In the example shown in FIG. 3, the connection element 44 has a surface44 a on the side of the substrate 30, a surface 44 b on the side opposedto the substrate 30, and side surfaces 44 c and 44 d. The connectionelement 44 has substantially a rectangular section in general. A width Wof the connection element 44, i.e., the width W along the sheet plane ofthe substrate 30 is preferably not less than 1 μm and not more than 15μm. Since the connection element 44 having such a width W issufficiently thin, the conductive pattern 40 can be effectively madeinvisible. In addition, a height (thickness) H of the connection element44, i.e., the height (thickness) H along the normal direction to thesheet plane of the substrate 30 is preferably not less than 1 μm and notmore than 20 μm. Further, the height H of the connection element 44 ismore preferably not less than 2 μm and not more than 20 μm. The height(thickness) of the connection element 44 can be said as a height(thickness) of the conductive pattern 40. Due to the connection element44 having such a thickness (height) H, a sufficient conductivity can beensured while a suitable resistance value is provided.

According to the above-described conductive pattern 40, as shown in FIG.6, light incident on the side surface of the connection element 44having a shape other than a linear shape (straight line segment), suchas an arcuate shape, a polygonal line shape, a corrugated shape and soon, is reflected irregularly on the side surface. Thus, it can berestrained that the light incident on the side surface of the connectionelement 44 from a certain direction is reflected on the side surface ina certain direction correspondingly to the incident direction. Thus, itcan be restrained that the reflected light is visible to an observer, sothat the conductive pattern 40 having the connection elements 44 isvisible to the observer. In particular, a rate of the connectionelements 44, which are straight lines (straight line segments)connecting the two branch points 42, relative to the plurality ofconnection elements 44, is less than 20%. That is to say, 80% or more ofthe plurality of connection elements 44 have a shape other than a linearshape (straight line segment), such as an arcuate shape, a polygonalline shape, a corrugated shape and so on. In this case, it can be moreeffectively restrained that light reflected on the side surface of theconnection element 44 is visible to an observer, so that the conductivepattern 40 having the connection elements 44 is visible to the observer.

In addition, when the connection element 44 has the height (thickness) Hof not less than 1 μm, in particular, when the connection element 44 hasthe height H of not less than 2 μm, the light reflected on the sidesurface of the connection element 44 is more likely to be visible to anobserver. Thus, in this case, in order to restrain that the lightreflected on the side surface of the connection element 44 is visible tothe observer, it is particularly effective that a rate of the connectionelements 44, which are straight lines (straight line segments)connecting the two branch points 42, relative to the plurality ofconnection elements 44, is made to be less than 20%.

Further, when a distribution of the opening areas 43 is sparse so thatan average length D_(ave) between centers of gravity between the twoadjacent opening areas 43 is longer, the length of each connectionelement 44 is also longer. When the length of each connection element 44is longer, light reflected on the side surface of the connection element44 in a certain direction is more visible. According to the research ofthe present inventors, when the average distance D_(ave) between thecenters of gravity between the two adjacent opening areas 43 is 80 μm ormore, light reflected on the side surface of the connection element 44tends to be visible to an observer. The average distance D_(ave) may be70 μm or more. Thus, in this case, in order to restrain that the lightreflected on the side surface of the connection element 44 is visible tothe observer, it is particularly effective that a rate of the connectionelements 44, which are straight lines (straight line segments)connecting the two branch points 42, relative to the plurality ofconnection elements 44, is made to be less than 20%. The two adjacentopening areas 43 mean two adjacent opening areas 43 which share oneconnection element 44. In addition, the distance D between centers ofgravity G₁, G₂ means a linear distance between the centers of gravityG₁, G₂.

The average distance D_(ave) between the centers of gravity between thetwo adjacent opening areas 43 is preferably 300 μm or less. When theaverage distance D_(ave) between the centers of gravity between the twoadjacent opening areas 43 is not less than 80 μm and not more than 300μm, a line width of the connection element (thin conductive wire) 44 canbe sufficiently thinned so as to be invisible, and calorific values atrespective positions of the conductive pattern 40 can be sufficientlymade uniform.

In the example shown in FIG. 3, the connection element 44 includes afirst dark color layer 63 disposed on the substrate 30, a conductivemetal layer 61 disposed on the first dark color layer 63, and a seconddark color layer 64 disposed on the conductive metal layer 61. In otherwords, the surface of the conductive metal layer 61, which is located onthe side of the substrate 30, is covered with the first dark color layer63, and the surface of the conductive metal layer 61, which is locatedon the side opposed to the substrate 30, and both the side surfacesthereof are covered with the second dark color layer 64. The dark colorlayer 63, 64 may be a layer having a visible light reflectance lowerthan that of the conductive metal layer 61. For example, the dark colorlayer 63, 64 is a layer of a dark color such as black color. Owing tothe dark color layers 63, 64, the conductive meal layer 61 can be moreinvisible, whereby a field of view of a passenger can be more suitablyensured.

Next, an example of a manufacturing method of the heating plate 10 isdescribed with reference to FIGS. 7 to 13. FIGS. 7 to 13 are sectionalviews showing the example of the manufacturing method of the heatingplate 10 in sequence.

Firstly, the sheet-like substrate 30 is prepared. The substrate 30 is anelectrically insulating resin substrate that transmits light of awavelength (380 nm to 780 nm) of a visible light wavelength band, whichis generally recognized as transparent.

Then, as shown in FIG. 7, the first dark color layer 63 is disposed onthe substrate 30. For example, the first dark color layer 63 can bedisposed on the substrate 30 by a plating method including electrolyticplating and electroless plating, a spattering method, a CVD method, aPVD method, an ion plating method or a combination method of the two ormore methods. Various known materials may be used as material of thefirst dark color layer 63. For example, the material may be coppernitride, copper oxide, nickel nitride and so on.

Next, as shown in FIG. 8, the conductive metal layer (conductive layer)61 is disposed on the first dark color layer 63. As described above, theconductive metal layer 61 is a layer made of one or more of gold,silver, copper, platinum, aluminum, chrome, molybdenum, nickel,titanium, palladium, indium, tungsten and an alloy thereof. Theconductive metal layer 61 may be formed by a known method. For example,there is employed a method of adhering a metal foil such as a copperfoil by means of a weather-resistant adhesive or the like, a platingmethod including electrolytic plating and electroless plating, aspattering method, a CVD method, a PVD method, an ion plating method ora combination method of the two or more methods.

When the conductive metal layer 61 is formed of a metal foil such as acopper foil, the following method may be employed. Namely, the firstcolor layer 63 is formed previously on one surface of the metal foil inadvance. Then, the metal foil with the first dark color layer 63 islaminated on the substrate 30 through an adhesive layer or a gluinglayer (pressure sensitive adhesive layer), such that the first colorlayer 63 faces the substrate 30. In this case, the first dark colorlayer 63 may be formed as follows. By subjecting a part of a materialconstituting the metal foil to a darkening treatment (blackeningtreatment), the first dark color layer 63 made of metallic oxide ormetallic sulfide can be formed from the part constituting the metalfoil. Alternatively, the first dark color layer 63 as a coating filmmade of a dark color material or a plated layer made of nickel or chromemay be disposed on a surface of the metal foil. In addition, the surfaceof the metal foil may be roughened, and the first dark color layer 63may be disposed thereon.

Then, as shown in FIG. 9, a resist pattern 62 is disposed on theconductive metal layer 61. The resist pattern 62 is a pattern thatcorresponds to a pattern of the conductive pattern 40 to be formed. Inthe method described herein, the resist pattern 62 is disposed only on aportion where the conductive pattern 40 is finally to be formed. Theresist pattern 62 may be formed by a pattering method using a knownphotolithographic technique.

Then, as shown in FIG. 10, the conductive metal layer 61 and the firstdark color layer 63 are etched with the resist pattern 62 serving as amask. Due to this etching process, the conductive metal layer 61 and thefirst color layer 63 can be patterned substantially similar to theresist pattern 62. The etching method is not particularly limited, and aknown method may be employed. The known method may be a wet etchingmethod using etchant, a plasma etching method and so on. Thereafter, asshown in FIG. 11, the resist pattern 62 is removed.

After that, as shown in FIG. 12, the second dark color layer 64 isformed on the surface 44 b of the conductive metal layer 61 on the sideopposed to the substrate 30 and the side surfaces 44 c, 44 d. The seconddark color layer 64 may be formed as follows. By subjecting a part of amaterial constituting the conductive metal layer 61 to a darkeningtreatment (blackening treatment), the second dark color layer 64 made ofmetallic oxide or metallic sulfide can be formed from the partconstituting the conductive metal layer 61. Alternatively, the seconddark color layer 64 as a coating film made of a dark color material or aplated layer made of nickel or chrome may be disposed on a surface ofthe metal foil. In addition, the surface of the conductive metal layer61 may be roughened, and the second dark color layer 64 may be disposedthereon.

In the manner as described above, the conductive pattern sheet 20 shownin FIG. 12 is manufactured.

Finally, the glass plate 11, the joint layer 13, the conductive patternsheet 20, the joint layer 14 and the glass plate 12 are superposed inthis order, and heated/pressurized. In the example shown in FIG. 13,firstly, the joint layer 13 is provisionally attached to the glass plate11, and the joint layer 14 is provisionally attached to the glass plate12. Then, the glass plate 11 to which the joint layer 13 has beenprovisionally attached, the conductive pattern sheet 20, the glass plate12 to which the joint layer 14 has been provisionally attached, aresuperposed in this order and heated/pressurized, in such a manner thatthe side of the glass plate 11, to which the joint layer 13 has beenprovisionally attached, and the side of the glass plate 12, to which thejoint layer 14 has been provisionally attached, face the conductivepattern sheet 20. Thus, the glass plate 11, the conductive pattern sheet20 and the glass plate 12 are joined through the joint layers 13, 14, sothat the heating plate 10 shown in FIG. 3 is manufactured.

The aforementioned heating plate 10 in the first embodiment includes thepair of glass plates 11, 12, the conductive pattern 40 disposed betweenthe pair of glass plates 11, 12 and defining the plurality of openingareas 43, and the joint layers 13, 14 disposed between the conductivepattern 40 and at least one of the pair of glass plates 11, 12. Theconductive pattern 40 includes the plurality of connection elements 44that extend between the two branch points 42 to define the opening areas43. A rate of the connection elements 44, which are straight linesegments connecting the two branch points 42, relative to the pluralityof connection elements 44, is less than 20%.

According to such a heating plate 10, as shown in FIG. 6, light incidenton the side surface of the connection element 44 having a shape otherthan a linear shape (straight line segment), such as an arcuate shape, apolygonal line shape, a corrugated shape and so on, is reflectedirregularly on the side surface. Thus, it can be restrained that thelight incident on the side surface of the connection element 44 from acertain direction is reflected on the side surface in a certaindirection correspondingly to the incident direction. Thus, it can berestrained that the reflected light is visible to an observer, so thatthe conductive pattern 40 having the connection elements 44 is visibleto the observer.

The above first embodiment can be variously modified. Modificationexamples are described herebelow with reference suitably to thedrawings. In the below description and the drawings for the description,a component that can be similarly made as the above embodiment is shownby the same symbol as a component corresponding to the above embodiment,and overlapped description is omitted.

A modification example of the manufacturing method of the heating plate10 is described with reference to FIGS. 14 to 18. FIGS. 14 to 18 aresectional views showing the modification example of the manufacturingmethod of the heating plate 10 in sequence.

Firstly, the conductive pattern sheet 20 is manufactured. The conductivepattern sheet 20 may be manufactured by the method as described above inthe example of the manufacturing method of the heating plate 10.

Then, the glass plate 11, the joint layer 13 and the conductive patternsheet 20 are superposed in this order, and heated/pressurized. In theexample shown in FIG. 14, the joint layer 13 is provisionally attachedto the glass plate 11 firstly. Then, the glass plate 11 to which thejoint layer 13 has been provisionally attached is superposed from theside of the conductive pattern 40 of the conductive pattern sheet 20 andheated/pressurized, in such a manner that the side of the glass plate11, to which the joint layer 13 has been provisionally attached, facesthe conductive pattern sheet 20. Thus, as shown in FIG. 15, the glassplate 11 and the conductive pattern sheet 20 are joined (provisionallyjoined or completely joined) through the joint layer 13.

Then, as shown in FIG. 16, the substrate 30 of the conductive patternsheet 20 is removed. For example, during the manufacture of theconductive pattern sheet 20, a peeling layer is formed on the substrate30, and the conductive pattern 40 is formed on the peeling layer.Preferably, the peeling layer is not removed in the step in which theconductive metal layer 61 and the first dark color layer 63 are etched.In this case, the substrate 30 is joined to the conductive pattern 40and the joint layer 13 through the peeling layer. In the step in whichthe substrate 30 is removed from the conductive pattern sheet 20, thesubstrate 30 of the conductive pattern sheet 20 is peeled from theconductive pattern 40 and the joint layer 13 by means of the peelinglayer.

The peeling layer may be, for example, a peeling layer of an interfacepeeling type, a peeling layer of an interlayer peeling type, a peelinglayer of a cohesion peeling type and so on. As a peeling layer of aninterface peeling type, there may be suitably used a peeling layerhaving relatively a lower adhesive property to the conductive pattern 40and the joint layer 13, than an adhesive property to the substrate 30.Such a layer may be a silicone resin layer, a fluororesin layer, apolyolefin resin layer and so on. In addition, it is possible to use apeeling layer having relatively a lower adhesive property to thesubstrate 30, than an adhesive property to the conductive pattern 40 andthe joint layer 13. A peeling layer of an interlayer peeling type maybe, for example, a peeling layer including a plurality of film layers,and having relatively a lower adhesive property between the plurality oflayers, than an adhesive property to the conductive pattern 40, thejoint layer 13 and the substrate 30. A peeling layer of a cohesionpeeling type may be, for example, a peeling layer formed by dispersingfillers as a dispersal phase in a base resin as a continuous phase.

When a peeling layer of an interface peeling type including a layerhaving relatively a lower adhesive property to the conductive pattern 40and the joint layer 13, than an adhesive property to the substrate 30,is used, a peeling phenomenon occurs between the peeling layer, and theconductive pattern 40 and the joint layer. In this case, it is possibleto make the peeling layer not remain on the conductive pattern 40 andthe joint layer 13. Namely, the substrate 30 is removed together withthe peeling layer. When the substrate 30 and the peeling layer areremoved in this manner, the joint layer 13 is exposed into the openingareas 43 of the conductive pattern 40.

On the other hand, when a peeling layer of an interface peeling typehaving relatively a lower adhesive property to the substrate 30, than anadhesive property to the conductive pattern 40 and the joint layer 13,is used, a peeling phenomenon occurs between the peeling layer and thesubstrate 30. When a peeling layer of an interlayer peeling typeincluding a plurality of film layers, and having relatively a loweradhesive property between the plurality of layers, than an adhesiveproperty to the conductive pattern 40, the joint layer 13 and thesubstrate 30, is used, a peeling phenomenon occurs between the pluralityof layers. When a peeling layer of a cohesion peeling type, which isformed by dispersing fillers as a dispersal phase in a base resin as acontinuous phase, is used, a peeling phenomenon occurs in the peelinglayer by cohesion failure.

Finally, the glass plate 11, the joint layer 13 and the conductivepattern 40, the joint layer 14, and the glass plate 12 are superposed inthis order, and heated/pressurized. In the example shown in FIG. 17, thejoint layer 14 is attached to the glass plate 12 firstly. Then, theglass plate 11, the conductive pattern 40 and the joint layer 13, andthe glass plate 12 to which the joint layer 14 has been provisionallyattached are superposed in this order and heated/pressurized, in such amanner that the side of the glass plate 12, to which the joint layer 14has been provisionally attached, faces the conductive pattern 40 and thejoint layer 13. Thus, the glass plate 11, the conductive pattern 40, theglass plate 12 are joined (completely joined) through the joint layers13, 14, whereby the heating plate 10 shown in FIG. 18 is manufactured.

According to the heating plate 10 shown in FIG. 18, the heating plate 10can be free of substrate 30. Thus, the thickness of the heating plate 10as a whole can be reduced. In addition, the number of boundary faces inthe heating plate 10 can be reduced. Thus, deterioration of opticalproperties, i.e., deterioration of visibility can be restrained.

Next, another modification example of the manufacturing method of theheating plate 10 is described with reference to FIGS. 19 and 20. FIGS.19 and 20 are sectional views showing the other modification example ofthe manufacturing method of the heating plate 10 in sequence.

Firstly, by the same steps as those of the above modification example ofthe manufacturing method of the heating plate 10, the glass plate 11 andthe conductive pattern sheet 20 are joined (provisionally joined)through the joint layer 13. Then, the substrate 30 is removed therefrom.Namely, the laminate of glass plate 11, the conductive pattern 40 andthe joint layer 13 is obtained, which is described in the abovemodification example of the manufacturing method of the heating plate 10with reference to FIG. 16.

Then, as shown in FIG. 19, the glass plate 11, the joint layer 13 andthe conductive pattern 40, and the glass plate 12 are superposed in thisorder, and heated/pressurized. Thus, the glass plate 11 and theconductive pattern 40 are joined (completely joined) through the jointlayer 13, and the glass plate 11 and the glass plate 12 are joined(completely joined) through the joint layer 13. Thus, the heating plate10 shown in FIG. 20 is manufactured.

According to the heating plate 10 shown in FIG. 20, the heating plate 10can be free of the substrate 30 and the joint layer 14. Thus, thethickness of the heating plate 10 as a whole can be further reduced. Inaddition, the number of boundary faces in the heating plate 10 can befurther reduced. Thus, deterioration of optical properties, i.e.,deterioration of visibility can be furthermore effectively restrained.Moreover, since the conductive pattern 40 and the glass plate 12 are incontact with each other, a heating efficiency of the glass plate 12 bythe conductive pattern 40 can be increased.

As another modification example, FIG. 21 shows a modification example ofthe reference pattern. As shown in FIG. 21, a reference pattern 80 is amesh-like pattern defining a number of opening areas 83. The referencepattern 80 includes a plurality of line segments 84 that extend betweentwo branch points 82 to define the opening areas 83. Namely, thereference pattern 80 is an aggregation of a number of the line segments84 each forming the branch points 82 at both ends thereof. Particularlyin the illustrated example, the reference pattern 80 has a shapeobtained by elongating the reference pattern 50 shown in FIG. 4 along afirst direction (X). In other words, the reference pattern 80 has ashape obtained by compressing the reference pattern 50 shown in FIG. 4along a second direction (Y) perpendicular to the first direction (X).

A part of a conductive pattern 70, which is determined by the methoddescribed above with reference to FIG. 5, based on the reference pattern80 is shown in enlargement in FIG. 22 together with a corresponding partof the reference pattern 80. In the example shown in FIG. 22, theconductive pattern 70 includes a plurality of branch points 72 arrangedon the respective branch points 82 of the reference pattern 80, and aplurality of connection elements 74 that extend between the two branchpoints 72 to define opening areas 73. A rate of the connection elements74, which are straight lines (straight line segments) connecting the twobranch points 72, relative to the plurality of connection elements 74,is less than 20%. The conductive pattern 70 has a mesh-like pattern onwhich the plurality of connection elements 74 are arrangedcorrespondingly to the respective line segments 84 of the referencepattern 80.

In the example shown in FIG. 22, an average of ratio (L₁/L₂) of a lengthL₁ of each opening area 73 of the conductive pattern 70 along the firstdirection (X), relative to a length L₂ of the opening area 73 along thesecond direction (Y) perpendicular to the first direction (X), is notless than 1.3 and not more than 1.8. When the conductive pattern 70includes the opening area 73 of such a dimension, light reflected on theside surface of the connection element 74 is more likely to be visibleto an observer. Thus, in this case, in order to restrain that the lightreflected on the side surface of the connection element 74 is visible tothe observer, it is particularly effective that a rate of the connectionelements, which are straight lines (straight line segments) connectingthe two branch points 72, relative to the plurality of connectionelements 74 is made to be less than 20%.

It is not necessary to specify the respective dimensions of theconductive pattern 40, 70, such as an average distance D_(ave) betweencenters of gravity of the two adjacent opening areas 43, and an averageof ratio (L₁/L₂) of a length L₁ of each opening area 73 of theconductive pattern 70 along the first direction (X) relative to a lengthL₂ of the opening area 73 along the second direction (Y) perpendicularto the first direction (X), by checking all the areas of the conductivepattern 40, 70 and calculating average values. Actually, it is possibleto check the suitable number of elements to be checked (an averagedistance D_(ave) between centers of gravity of the two adjacent openingareas 43, and an average of ratio (L₁/L₂) of a length L₁ of each openingarea 73 of the conductive pattern 70 along the first direction (X)relative to a length L₂ of the opening area 73 along the seconddirection (Y) perpendicular to the first direction (X)) in considerationof dispersion degree of elements to be checked, in a certain sectionhaving a planar dimension (an area) that is considered to be capable ofreflecting a general tendency of the elements to be checked, andcalculate average values. Values which were thus specified can behandled as an average distance D_(ave) between centers of gravity of thetwo adjacent opening areas 43, and an average of ratio (L₁/L₂) of alength L₁ of each opening area 73 of the conductive pattern 70 along thefirst direction (X) relative to a length L₂ of the opening area 73 alongthe second direction (Y) perpendicular to the first direction (X). Inthe conductive pattern 40, 70 in this embodiment, by observing 100points included in an area of 300 mm×300 mm by means of an opticalmicroscope or an electron microscope, and calculating average values,respective dimensions of the conductive pattern 40, 70 can be specified.

As an anther modification example, in the above-described firstembodiment, the conductive pattern 40, 70 has a pattern determined basedon the Voronoi diagram, i.e., a number of the opening areas 53, 83 whichhave shapes which do not have a repeated regularity (periodicregularity) and are arranged at pitches which do not have a repeatedregularity (periodic regularity). However, not limited to this pattern,there may be used, as the conductive pattern, various patterns such as apattern in which triangular, rectangular, or hexagonal opening areas ofthe same shape are regularly arranged, a pattern in which opening areasof different shapes are regularly arranged, and so on.

In addition, in the example shown in FIGS. 7 to 20, the second darkcolor layer 64 provides the surface 44 b of the connection element 44,which is opposed to the substrate 30, and the side surfaces 44 c, 44 dthereof. However, not limited thereto, the second dark color layer 64may provide only the surface 44 b of the connection element 44, which isopposed to the substrate 30, or the side surfaces 44 c, 44 d thereof.When the second dark color layer 64 provides only the surface 44 b ofthe connection element 44, which is opposed to the substrate 30, thesecond dark color layer 64 and the resist pattern 62 are disposed inthis order on the conductive metal layer (conductive layer) 61, afterthe step shown in FIG. 8, for example. Thereafter, the second dark colorlayer 64, the conductive metal layer 61 and the first dark color layer63 may be etched with the resist pattern 62 serving as a mask.Alternatively, when the second dark color layer 64 provides only theside surfaces 44 c, 44 d of the connection element 44, the second darkcolor layer 64 is formed without removing the resist pattern 62, afterthe step shown in FIG. 10, for example, and thereafter the resistpattern 62 is removed. When the first dark color layer 63 is notnecessary, the step of disposing the first dark color layer 63 on thesubstrate 30, which is shown in FIG. 7, may be omitted.

The heating plate 10 may be used in a rear window, a side window and asun roof of the automobile 1. In addition, the heating plate 10 may beused in a window of a vehicle other than an automobile, such as arailway (train), an aircraft, a vessel, a space vessel and so on.

Further, in addition to a vehicle, the heating plate 10 may be used in apart by which an inside and an outside is partitioned, such as a windowof a building, a store and a house.

Although some modification examples of the above first embodiment aredescribed, the modification examples can be naturally combined with oneanother for application.

Second Embodiment

FIG. 1 and FIGS. 24 to 42 are views for explaining a second embodimentaccording to the present invention. In the second embodiment describedbelow, a component corresponding to that of the first embodiment isshown by a symbol in 100 s with the same last two digits, and overlappeddescription is omitted.

FIG. 24 is a view of a heating plate when viewed in a normal directionof a plate plane thereof. FIG. 25 is a sectional view of the heatingplate of FIG. 24. The heating plate in this embodiment is sometimesreferred to as “laminated glass”.

FIG. 24 shows a heating plate 110 when viewed in a normal direction of aplate plane thereof. FIG. 25 is a cross-sectional view corresponding toa XXV-XXV line of the heating plate 110 of FIG. 24. In the example shownin FIG. 25, the heating plate 110 includes a pair of glass plates 111,112, a conductive pattern sheet (pattern sheet) 120 disposed between thepair of glass plates 111, 112, a joint layer 113 that joins the glassplate 111 and the conductive pattern sheet 120, and a joint layer 114that joins the glass plate 112 and the conductive pattern sheet 120. Inthe example shown in FIGS. 1 and 24, the heating plate 110 is curved.However, FIGS. 25 and 35 to 42 planarly show the heating plate 110 andthe glass plates 111, 112, for simplifying the illustration andfacilitating the understanding.

The conductive pattern sheet 120 includes a sheet-like substrate 130, aholding layer 131 laminated on the substrate 130, a conductive pattern(conductive pattern member) 140 formed on the holding layer 131, awiring part 15 for powering the conductive pattern 140, and a connectionpart 16 connecting the conductive pattern 140 and the wiring part 15.

In the example shown in FIGS. 24 and 25, the conductive pattern 140 ispowered by a power source 7, such as a battery, through the wiring part15 and the connection part 16, so that the conductive pattern 140generates heat by means of resistance heat. The heat generated by theconductive pattern 140 is transmitted to the glass plates 111, 112through the joint layers 113, 114, so that the glass plates 111, 112 arewarmed up. Thus, dew drops on the glass plates 111, 112 can be removedso that the glass plates 111, 112 can be defogged. When there is snow orice on the glass plates 111, 112, the snow or ice can be unfrozen. Thus,an excellent field of view of a passenger can be ensured.

Particularly when used as a front window of an automobile, the glassplate 111, 112 preferably has a high visible light transmittance, inorder not to hinder a field of view of a passenger. A material of such aglass plate 111, 112 may be soda lime glass, blue plate glass and so on,for example. The glass plate 111, 112 preferably has a transmittance of90% or more in a visible light area. The visible light transmittance isspecified as follows. The visible light transmittance of the glass plate111, 112 is specified as follows. Transmittance of light withmeasurement wavelength range of from 380 nm to 780 nm is measured byusing a spectrophotometer (manufactured by Shimadzu Corporation,“UV-3100PC”, compliant with JIS K 0115). The visible light transmittanceis an average value of the transmittances at the respective wavelengths.The visible light transmittance may be lowered by partially or totallycoloring the glass plate 111, 112, for example. In this case, directsunlight can be shielded and an inside of the automobile is less visiblefrom outside.

In addition, the glass plate 111, 112 preferably has a thickness of notless than 1 mm and not more than 5 mm. With such a thickness, the glassplate 111, 112 excellent in strength and optical properties can beobtained.

The glass plates 111, 112 and the conductive pattern sheet 120 arejoined to each other through the joint layers 113, 114, respectively. Assuch a joint layer 113, 114, a layer made of a material having variousadhesion properties or gluing (pressure sensitive adhesive) properties.In addition, the joint layer 113, 114 preferably has a high visiblelight transmittance. A typical joint layer may be a layer made ofpolyvinyl butyral (PVB), for example. The joint layer 113, 114preferably has a thickness of not less than 0.15 mm and not more than0.7 mm.

Not limited to the illustrated example, the heating plate 110 may beprovided with another function layer for exerting a specific function.In addition, one function layer may exert two or more functions.Alternatively, for example, a function may be given to at least one ofthe glass plate 111, 112 of the heating plate 110, the joint layer 113,114 thereof, and the substrate 130 of the conductive pattern sheet 120thereof, which is described later. The function that can be given toheating plate 110 may be an antireflection (AR) function, a hard coat(HC) function having an abrasion resistance, an infrared ray shield(reflection) function, an ultraviolet ray shield (reflection) function,a polarizing function, an antifouling function and so on, for example.

Next, the conductive pattern sheet 120 is described. The conductivepattern sheet 120 includes the sheet-like substrate 130, the holdinglayer 131 laminated on the substrate 130, the conductive pattern 140formed on the holding layer 131, the wiring part 15 for powering theconductive pattern 140, and the connection part 16 connecting theconductive pattern 140 and the wiring part 15. The conductive patternsheet 120 may have a planar dimension (an area) substantially the sameas that of the glass plate 111, 112 so as to be placed all over theheating plate 110. Alternatively, the conductive pattern sheet 120 maybe placed over only a part of the heating plate 110, such as a part infront of a driver's seat.

The sheet-like substrate 130 functions as a substrate that supports theholding layer 131 and the conductive pattern 140. The substrate 130 isan electrically insulating substrate that transmits light of awavelength (380 nm to 780 nm) of a visible light wavelength band, whichis generally recognized as transparent. In the example shown in FIGS.24, 26 and 27, the substrate 130 has substantially the same dimensionsas those of the glass plate 111, 112 and has substantially a trapezoidalplanar shape.

Any resin can be used as a resin to be contained in the substrate 130,as long as it transmits visible light and can suitably support theholding layer 131 and the conductive pattern 140. Preferably, athermoplastic resin may be used. The thermoplastic resin may be an acrylresin made of, e.g., polymethyl methacrylate, a polyester resin made of,e.g., polyvinyl chloride, polyethylene terephthalate or amorphouspolyethylene terephthalate (A-PET), a polyethylene resin, a polyolefinresin made of, e.g., polypropylene, a cellulose-based resin made of,e.g., triacetyl cellulose (cellulose triacetate), a polystyrene orpolycarbonate resin, an AS resin and so on, for example. In particular,an acryl resin and a polyvinyl chloride are preferred because of theirexcellent etching resistance, weather resistance and light resistance.

In addition, in consideration of support property and light transmissionof the conductive pattern 140, the substrate 130 preferably has athickness of not less than 0.03 mm and not more than 0.3 mm.

The holding layer 131 has a function for improving a joint propertybetween the substrate 130 and the conductive pattern 140 to hold theconductive pattern 140. The holding layer 131 may be formed either bylaminating a transparent electrically insulating resin sheet with thesubstrate 130 or by coating the substrate 130 with a resin material. Theholding layer 131 may be made of, e.g., polyvinyl butyral (PVB), atwo-pack curable urethane adhesive, or a two-pack curable epoxyadhesive. In addition, as described below, when the conductive patternsheet 120 is joined (provisionally joined) to the glass plate 111through the joint layer 113 and then the substrate 130 is peeled, theholding layer 131 may include a peeling layer. A thickness of theholding layer 131 may be not less than 1 μm and not more than 100 μm, inconsideration of a light transmission and a joint property to thesubstrate 130 and the conductive pattern 140. Preferably, the thicknessof the holding layer 131 may be not less than 1 μm and not more than 15μm.

The conductive pattern 140 is described with reference to FIGS. 26 to28. FIGS. 26 and 27 are plan views of the conductive pattern sheet 120when viewed in a normal direction of a sheet plane thereof. FIG. 28 is aview showing in enlargement a part of the conductive pattern 140 of FIG.27.

The conductive pattern 140 is powered by the power source 7, such as abattery, through the wiring part 15 and the connection part 16, so as togenerate heat by means of resistance heat. The heat is transmitted tothe glass plates 111, 112 through the joint layers 113, 114, so that theglass plates 111, 112 are warmed up.

FIG. 26 shows an example of a pattern shape of the conductive pattern140. In the example shown in FIG. 26, the conductive pattern 140includes a plurality of thin conductive wires 141 connecting a pair ofthe connection parts 16. In the illustrated example, each of theplurality of thin conductive wires 141 extends in a corrugated patternfrom the one connection part 16 to the other connection part 16. Thethin conductive wires 141 are arranged apart from one another in adirection not in parallel with a direction in which the thin conductivewires 141 extend. In particular, the thin conductive wires 141 arearranged perpendicular to the direction in which the thin conductivewires 141 extend. In place of the corrugated shape, each thin conductivewire 141 may extend between the pair of connection parts 16 in a linearpattern, a polygonal line pattern or a sine wave pattern. The thinconductive wires 141, which are adjacent to each other in a directionnot in parallel with the direction in which the thin conductive wires141 extend, may be connected via a thin wire, i.e., a connection wire.

FIGS. 27 and 28 show another example of a pattern shape of theconductive pattern 140. In the example shown in FIGS. 27 and 28, thethin conductive wires 141 of the conductive pattern 140 are arranged ina mesh-like pattern defining a number of opening areas 144. Theconductive pattern 140 includes a plurality of connection elements 145that extend between two branch points 143 to define the opening areas144. Namely, the reference pattern 140 is an aggregation of a number ofthe connection elements 145 each forming the branch points 143 at bothends thereof.

In the example shown in FIGS. 27 and 28, a number of the opening areas144 of the conductive pattern 140 have shapes which do not have arepeated regularity (periodic regularity) and are arranged at pitcheswhich do not have a repeated regularity (periodic regularity).Particularly in the illustrated example, the opening areas 144 arearranged so as to correspond to respective Voronoi areas in a Voronoidiagram obtained from generatrix points whose position coordinates in aplane have a predetermined random two-dimensional distribution. Theserandomly distributed generatrix points have a feature in which adistance between two adjacent generatrix points is distributed between apredetermined upper limit value and a predetermined lower limit value.In other words, the respective connection elements 145 of the conductivepattern 140 correspond to respective boundaries of the Voronoi areas insuch a Voronoi diagram. In addition, the respective branch points 143 ofthe conductive pattern 140 correspond to Voronoi points in the Voronoidiagram. Since the Voronoi diagram can be obtained by the known methodsdisclosed in JP2012-178556A and JP2013-238029A, for example, a detaileddescription of the method of creating the Voronoi diagram is omittedherein.

When a conductive pattern has a number of opening areas that have shapeshaving a repeated regularity (periodic regularity), such as a tetragonallattice arrangement or a honeycomb arrangement, and are arranged atpitches having a repeated regularity (periodic regularity), light beamstripes are sometimes visible because of the repeated regularity of thearrangement of the opening areas. These visible light beam stripes arecaused when light enters a heating plate from a side opposite to anobserver, e.g., when light of a headlight of an oncoming automobileenters a front window of the automobile, the light is dispersed to lightbeam stripes along a predetermined pattern such as a stripe pattern onthe heating plate so that the light beam stripes can be seen. Inparticular, when a number of the opening areas of the conductive patternhave shapes having a repeated regularity and are arranged at pitcheshaving a repeated regularity, such light beam stripes tend to be easilyvisible. The fact that the light beam stripes are visible to an observersuch as a driver deteriorates a visibility of the observer through thepane. On the other hand, as shown in FIGS. 27 and 28, the conductivepattern 140 having a number of the opening areas 144 of the conductivepattern 140 have shapes which do not have a repeated regularity and arearranged at pitches which do not have a repeated regularity caneffectively restrain generation of light beam stripes in the heatingplate 110.

In the conductive pattern 140 shown in FIGS. 27 and 28, an average ofthe number of the connection elements 145 extending from one branchpoint 143 is more than 3.0 and less than 4.0. When an average of thenumber of the connection elements 145 extending from one branch point143 is more than 3.0 and less than 4.0, an irregular honeycombarrangement pattern can be obtained. When an average of the number ofthe connection elements 145 extending from one branch point 143 is morethan 3.0 and less than 4.0, the arrangement of the opening areas 144 canbe made irregular whereby the presence of a direction in which theopening areas 144 are arranged with a repeated regularity (periodicregularity) can be prevented stably. As a result, generation of lightbeam stripes in the heating plate 110 can be more effectivelyrestrained. At the same time, since the connection elements 145 arearranged basically based on a honeycomb arrangement, the connectionelements 145 are uniformly dispersed so that non-uniform heat generationcan be effectively restrained.

Strictly speaking, an average of the number of connection elements 145extending from one branch point 143 is obtained by checking the numberof the connection elements 145 extending from all the branch points 143included in the conductive pattern 140, and by calculating an averagevalue. However, actually, considering a size of the one opening area 144defined by the thin conductive wires 141, it is possible to check thebranch points 143 the number of which is considered as suitable inconsideration of dispersion degree of elements to be checked, in acertain section having a planar dimension (an area) that is consideredto be capable of reflecting a general tendency of the number ofconnection elements 145 extending from the one branch point 143, andcalculate an average value thereof. An average value which was thusspecified can be handled as an average value of the number of connectionelements 145 extending from one branch point 143. For example, anaverage value obtained by counting and calculating the number ofconnection elements 145 extending from the 100 branch points 143included in an area of 300 mm×300 mm by means of an optical microscopeor an electron microscope, can be handled as an average of the number ofthe connection elements 145 extending from one branch point 143.

In the conductive pattern 140 shown in FIGS. 27 and 28, the conductivepattern 140 includes the opening areas 144 surrounded by the four, five,six or seven connection elements 145. Among the opening areas 144included in the conductive pattern 140, the number of opening areas 144surrounded by the six connection elements 145 is predominant. Namely, asto the opening areas 144 included in the conductive elements 145, thenumber of opening areas 144 surrounded by the six connection elements145 is larger than the number of the opening areas 144 surrounded by thefour, five or seven connection elements 145.

In such a conductive pattern 140, the arrangement of the opening areas144 is an irregular honeycomb arrangement in which the respectiveopening areas lack a regularity in shape and arrangement, as comparedwith a honeycomb arrangement in which in which hexagons of the sameshape are regularly arranged. In other words, the opening areas 144 arearranged such that shapes and positions of the respective opening areasare random, basically based on the honeycomb arrangement. Thus, it canbe restrained that the opening areas 144 are arranged too densely or toosparsely, whereby the opening areas 144 can be distributed atsubstantially uniform density, i.e., in a uniform manner. As a result,the heat generation non-uniformity can be effectively restrained. Inaddition, it is stably possible to make completely irregular thearrangement of the opening areas 144, i.e., to prevent the presence of adirection in which the opening areas 144 are regularly arranged. Thus,generation of light beam stripes in the heating plate 110 can be moreeffectively restrained.

Strictly speaking, the number of connection elements 145 surrounding oneopening area 144 is obtained by checking the number of connectionelements 145 surrounding all the opening areas 144 included in theconductive pattern 140. However, actually, considering a size of the oneopening area 144 defined by the thin conductive wires 141, it ispossible to check the opening areas 144 the number of which isconsidered to be suitable in consideration of the number of dispersiondegree of elements to be checked, in a certain section having a planardimension (an area) that is considered to be capable of reflecting ageneral tendency of the number of connection elements 145 surroundingone opening area 144, and multiply the number of opening areas 144 foreach number of the connection elements 145 surrounding the opening area144. For example, it can be judged which number of opening areas 144surrounded by the certain number of connection elements 145 included inthe conductive pattern 140 is the largest, by using a value obtained bycounting the number of connection elements 145 surrounding the 100opening areas 144 included in an area of 300 mm×300 mm by means of anoptical microscope or an electron microscope, and multiplying the numberof opening areas 144 for each number of the connection elements 145surrounding the opening area 144.

The material for constituting such a conductive pattern 140 may be oneor more of metal such as gold, silver, copper, platinum, aluminum,chrome, molybdenum, nickel, titanium, palladium, indium, tungsten, andan alloy of metals selected from two or more kinds of these metals, suchas nickel-chrome alloy, brass, bronze and so on, for example.

Next, a sectional shape of the thin conductive wire 141 of theconductive pattern 140 is described with reference to FIG. 29. FIG. 29is a view showing in enlargement a section of the conductive patternsheet 120 correspondingly to an A-A line in FIGS. 26 and 27.

In the example shown in FIG. 29, the conductive pattern sheet 120includes a sheet-like substrate 130, a holding layer 131 laminated onthe substrate 130, and a conductive pattern 140 formed on the holdinglayer 131. In a section (section shown in FIG. 29, which is referred toalso as “main cut plane” hereinafter) perpendicular to an extensiondirection (longitudinal direction) of the thin conductive wire 141, thethin conductive wire 141 has a proximal surface 141 b forming a surfaceon the side of the substrate 130, a distal surface 141 a facing theproximal surface 141 b, and side surfaces 141 c, 141 d connecting thedistal surface 141 a and the proximal surface 141 b. In this embodiment,the distal surface 141 a of the thin conductive wire 141 forms a firstsurface which finally faces one of the pair of glass plates 111, 112 ofthe heating plate 110, and the proximal surface 141 b of the thinconductive wire 141 forms a second surface which finally faces the otherof the pair of glass plates 111, 112 of the heating plate 110.

In the heating plate in which the conductive pattern 140 shown in FIG.29 is incorporated, i.e., in the heating plate 110 shown in FIG. 25,when a width of the first surface 141 a of the thin conductive wire 141along the plate plane of the heating plate 110 in the main cut plane isrepresented as W_(2a) (μm), a width of the second surface 141 b of thethin conductive wire 141 along the plate plane of the heating plate 110in the main cut plane is represented as W_(2b) (μm), and across-sectional area of the thin conductive wire 141 in the main cutplane is represented as S_(2a) (μm²), the following relationships aresatisfied.

0<IW _(2a) −W _(2b) I≦10  (a)

S _(2a)≧10  (b)

In the conductive pattern sheet 120 shown in FIG. 29, when a width ofthe proximal surface 141 b of the thin conductive wire 141 along thesheet plane of the conductive pattern sheet 120 in the main cut plane isrepresented as W_(2d) (μm), a width of the distal surface 141 a of thethin conductive wire 141 along the sheet plane of the conductive patternsheet 120 in the main cut plane is represented as W_(2c) (μm), and across-sectional area of the thin conductive wire 141 in the main cutplane is represented as S_(2b) (μm²), the following relationships aresatisfied.

0<IW _(2c) −W _(2d) I≦10  (c)

S _(2b)≧10  (d)

In the example shown in FIG. 29, the first surface (distal surface) 141a of the thin conductive wire 141 and the second surface (proximalsurface) 141 b thereof are in parallel. The one side surface 141 c ofthe thin conductive wire 141 forms a tapered surface that is tapered tocome close to the other side surface 141 d as a certain point in theside surface 141 c moves away from the substrate 130 along a normaldirection of the sheet plane of the conductive pattern sheet 120. Inaddition, the other side surface 141 d of the thin conductive wire 141forms a tapered surface that is tapered to come close to the one sidesurface 141 c as a certain point in the side surface 141 d moves awayfrom the substrate 130 along the normal direction of the sheet plane ofthe conductive pattern sheet 120. Thus, the thin conductive wire 141 isformed such that a line width thereof becomes narrow as a certain pointin the thin conductive wire 141 moves away from the substrate 130 alongthe normal direction of the sheet plane of the conductive pattern sheet120.

In the example shown in FIG. 25, when the conductive layer 140 isincorporated in the heating plate 110, the one side surface 141 c of thethin conductive wire 141 forms a tapered surface that is tapered to comeclose to the other side surface 141 d as a certain point in the sidesurface 141 c moves away from the glass plate 12 along a normaldirection of the plate plane of the heating plate 110. In addition, theother side surface 141 d of the thin conductive wire 141 forms a taperedsurface that is tapered to come close to the one side surface 141 c as acertain point in the side surface 141 d moves away from the glass plate112 along the normal direction of the plate plane of the heating plate110. Thus, the thin conductive wire 141 is formed such that the linewidth thereof becomes narrow as a certain point in the thin conductivewire moves away from the glass plate 112 along the normal direction ofthe plate plane of the heating plate 110.

Namely, the thin conductive wire 141 has substantially a trapezoidalshape in general, in the section perpendicular to its extensiondirection (longitudinal direction). In more detail, one side surface 141c of the thin conductive wire 141 has a shape that is concaved inward(toward the other side surface 141 d) from a line L₁ connecting one endA along a direction (which is referred to as width direction of the thinconductive wire 141 herebelow) in parallel with the sheet plane of theconductive pattern sheet 120 (plate plane of the heating plate 110) inthe first surface (distal surface) 141 a and perpendicular to theextension direction of the thin conductive wire 141, and one end B alongthe width direction of the thin conductive wire 141 in the secondsurface (proximal surface) 141 b. Similarly, the other side surface 141d of the thin conductive wire 141 has a shape that is concaved inward(toward the one side surface 141 c) from a line L₂ connecting the otherend C along the width direction of the thin conductive wire 141 in thefirst surface (distal surface) 141 a and the other end D along the widthdirection of the thin conductive wire 141 in the second surface(proximal surface) 141 b.

In the conductive pattern 140 as structured above, the widths W_(2a),W_(2c) of the first surface (distal surface) 141 a of the thinconductive wire 141 may be not less than 2 μm and not more than 13 μm.In addition, the width W_(2b), W_(2d) of the second surface (proximalsurface) 141 b of the thin conductive wire 141 may be not less than 5 μmand not more than 15 μm. Further, a height H of the thin conductive wire141, i.e., the height H along the normal direction of the plate plane ofthe heating plate 110 (sheet plane of the conductive pattern sheet 120)may be not less than 2 μm and not more than 15 μm. According to theconductive pattern 140 including the thin conductive wires 141 of suchdimensions, since each thin conductive wire 141 is sufficiently thin,the conductive pattern 140 can be effectively made invisible.

In the example shown in FIGS. 25 and 29, the width W_(2b) of the secondsurface 141 b of the thin conductive wire 141 (width W_(2d) of theproximal surface 141 b of the thin conductive wire 141) corresponds to amaximum width W of the thin conductive wire 141.

According to the conductive pattern 140 including the thin conductivewires 141 having the dimensions and the cross-sectional areas satisfyingthe relationships (a) and (b) or the relationships (c) and (d), it ispossible to ensure a cross-sectional area sufficient for obtaining asuitable conductivity, while reducing the maximum width W of the thinconductive wire 141. Thus, a suitable conductivity of the conductivepattern 140 can be obtained, while the conductive pattern 140 can beeffectively made invisible.

On the other hand, when a value of (IW_(2a)−W_(2b)I) or(IW_(2c)−W_(2d)I) is greater than 10 μm, it is necessary to increase themaximum width W of the thin conductive wire 141 in order to ensure asufficient cross-sectional area in terms of ensuring a suitableconductivity. In this case, the invisibility of the conductive pattern140 is deteriorated. In addition, when the maximum width W of the thinconductive wire 141 is reduced, a sufficient cross-sectional area cannotbe ensured so that an electric resistance of the conductive pattern 140becomes too large. Thus, the conductivity of the conductive pattern 140is deteriorated. That is to say, it is impossible to sufficiently ensurea suitable conductivity and to make invisible the conductive pattern 140at the same time.

As to the widths W_(2a), W_(2c) of the first surface (distal surface)141 a of the thin conductive wire 141, the widths W_(2b), W_(2d) of thesecond surface (proximal surface) 141 b of the thin conductive wire 141,and the height H of the thin conductive wire 141, actually it ispossible to measure the respective dimensions of the thin conductivewires 141 (connection elements 145) the number of which is considered tobe suitable in consideration of dispersion degree of elements to bechecked, in a certain section having a planar dimension (an area) thatis considered to be capable of reflecting a general tendency of therespective dimensions. For example, dimensions obtained by measuring the100 thin conductive wires 141 (connection elements 145) included in anarea of 300 mm×300 mm by means of an optical microscope or an electronmicroscope may be handled as the respective dimensions of the thinconductive wire 141 (connection element 145) of the conductive pattern140.

In the example shown in FIGS. 25 and 29, the thin conductive wire 141constituting the conductive pattern 140 includes a dark color layer 149located on the side of the substrate 130 of the thin conductive wire 141to form the second surface (proximal surface) 141 b of the thinconductive wire 141, and a conductive metal layer 148 located on theside opposed to the substrate 130 of the thin conductive wire 141 toform the first surface (distal surface) 141 a of the thin conductivewire 141. In other words, the surface of the conductive meal layer 148on the side of the substrate 130 is covered with the dark color layer149.

The dark color layer 149 may be provided by subjecting a part of amaterial constituting the conductive metal layer 148 to a darkeningtreatment (blackening treatment), and forming a coating film made ofmetallic oxide or metallic sulfide on the part of the conductive metallayer 148. The conductive metal layer 148 and the dark color layer 149have different etching speeds. In an etching step of the conductivemetal layer 148 and the dark color layer 149 using a photolithographictechnique as described below, by using the dark color layer 149, theetching speed of the conductive metal layer 148 can be suitablyadjusted. Since the dark color layer 149 formed by the darkeningtreatment (blackening treatment) has a roughened surface, the dark colorlayer 149 can exert an effect of improving contact between theconductive pattern 140 and the holding layer 131.

Next, an example of a manufacturing method of the heating plate 110 isdescribed with reference to FIGS. 30 to 35. FIGS. 30 to 35 are sectionalviews showing the example of the manufacturing method of the heatingplate 110 in sequence.

Firstly, a metal foil 151 is prepared, and a dark color film 152 isformed on one surface of the metal foil 151. The metal foil 151 willform the conductive metal layer 148 of the thin conductive wire 141. Thedark color film 152 will form the dark color layer 149 of the thinconductive wire 14. The metal foil 151 may be a foil made of metal suchas gold, silver, copper, platinum, aluminum, chrome, molybdenum, nickel,titanium, palladium, indium, and an alloy of metals selected from two ormore kinds of these metals, such as nickel-chrome alloy, brass and soon, for example. In addition, a thickness of the metal foil 151 may benot less than 2 μm and not more than 15 μm. The dark color film 152 maybe provided by subjecting a part of a material constituting the metalfoil 151 to a darkening treatment (blackening treatment), and forming acoating film made of metallic oxide or metallic sulfide on the part ofthe metal foil 151.

In addition, the substrate 130 is prepared, and the holding layer 131 isformed on one surface of the substrate 130. The substrate 130 may bemade of a thermoplastic resin transmitting visible light, for example.The thermoplastic resin may be an acryl resin made of, e.g., polymethylmethacrylate, a polyester resin made of, e.g., polyvinyl chloride,polyethylene terephthalate (PET), amorphous polyethylene terephthalate(A-PET) or polyethylene naphthalate (PEN), a polyolefin resin made of,e.g., polyethylene, polypropylene, polymethyl pentene or cyclicpolyolefin, a cellulose-based resin made of, e.g., triacetyl cellulose(cellulose triacetate), a polystyrene or polycarbonate resin, an ASresin and so on, for example. In particular, an acryl resin andpolyvinyl chloride are preferred because of their excellent etchingresistance, weather resistance and light resistance. The holding layer131 may be made of, e.g., polyvinyl butyral (PVB), a two-pack curableurethane adhesive, or a two-pack curable epoxy adhesive. The holdinglayer 131 may be formed by laminating a sheet-like material on thesubstrate 130, or may be formed by applying a flowable material to thesubstrate 130.

Then, as shown in FIG. 30, the metal foil 151 on which the dark colorfilm 152 has been formed and the substrate 130 on which the holdinglayer 131 has been formed are laminated in such a manner that the darkcolor film 152 and the holding layer 131 face to each other. At thistime, since the surface of the dark color film 152 in contact with theholding layer 131 is roughened by the darkening treatment (blackeningtreatment), the resin material constituting the holding layer 131 enterfine irregularities in the surface of the dark color film 152. Thus, thedark color film 152 and the holding layer 131 are securely joined toeach other by a so-called anchoring effect. Thus, the metal foil 151 andthe substrate 130 are securely joined to each other. Thus, as shown inFIG. 31, there is obtained a laminate in which the substrate 130, theholding layer 135, the dark color film 152 and the metal foil 151 aresuperposed in this order.

Next, as shown in FIG. 32, a resist pattern 155 is disposed on the metalfoil 151. The resist pattern 155 is a pattern corresponding to a patternof the conductive pattern 140 to be formed. In the method describedherein, the resist pattern 155 is disposed only a portion where theconductive pattern 140 is finally to be formed. The resist pattern 155may be formed by a patterning method using a known photolithographictechnique.

Then, as shown in FIG. 33, the metal foil 151 including the dark colorfilm 152 is etched (etched by corrosion) with the resist pattern 155serving as a mask. Due to this etching process, the metal foil 151including the dark color film 152 can be patterned substantially similarto the resist pattern 155. As a result, the conductive metal layer 148and the dark color layer 149, which will form the thin conductive wire141, is formed from the patterned metal foil 151. As a corrosionsolution used in the etching process, a known corrosion solution may besuitably selected and used depending on a material(s) of the metal foil151 and the dark color film 152 (if it exits). For example, when themetal foil 151 is made of copper and the dark color film 152 is made ofcopper oxide (II) (CuO), a ferric chloride solution may be used for boththe metal foil 151 and the dark color film 152. Alternatively, a ferricchloride solution may be used for a part (copper) forming the metal foil151, and diluted hydrochloric acid may be used for a part (copper oxide(II)) forming the dark color film 152.

Generally, as compared with the conductive metal layer 148 made of ametal material, the dark color layer 149 made of oxide or sulfide of themetal material is easily corroded by etching. Thus, as compared with thedark color layer 149, lateral corrosion by side etching is more likelyto proceed in the conductive metal layer 148. Thus, the lateralcorrosion by side etching is more likely to proceed in the conductivemetal layer 148 than in the dark color layer 149. In addition, also inthe conductive metal layer 148, the lateral corrosion by side etching ismore likely to proceed in an area distant from the dark color layer 149than in an area close to the dark color layer 149. Thus, by selecting anetchant and adjusting an etching period, the thin conductive wire 141can be manufactured, which has a width that changes to narrow from theside of the substrate 130 toward the resist pattern 155, i.e., which hasa tapered cross-sectional shape. Similarly, by selecting an etchant andadjusting an etching period, the widths W_(2a), W_(2c) of the firstsurface (distal surface) 141 a of the thin conductive wire 141 and thewidths W_(2b), W_(2d) of the second surface (proximal surface) 141 bthereof can be formed into desired widths.

Thereafter, the resist pattern 155 is removed so that the conductivepattern sheet 120 shown in FIG. 34 is manufactured.

Finally, the glass plates 111, the joint layer 113, the conductivepattern sheet 120, the joint layer 114 and the glass plate 112 aresuperposed in this order, and heated/pressurized. In the example shownin FIG. 35, the joint layer 113 is provisionally attached to the glassplate 111, and the joint layer 114 is provisionally attached to theglass plate 112. Then, the glass plate 111 to which the joint layer 113has been provisionally attached, the conductive pattern sheet 120, andthe glass plate 112 to which the joint layer 114 has been provisionallyattached are superposed in this order, and heated/pressurized, in such amanner that the side of the glass plate 111, to which the joint layer113 has been provisionally attached, and the side of the glass plate112, to which the joint layer 114 has been provisionally attached, facethe conductive pattern sheet 120. Thus, the glass plates 111, theconductive pattern sheet 120 and the glass plates 112 are joined throughthe joint layers 113, 114, whereby the heating plate 110 shown in FIG.25 is manufactured.

The aforementioned heating plate 110 in this embodiment includes thepair of glass plates 111, 112, the conductive pattern 140 disposedbetween the pair of glass plates 111, 112 and including the thinconductive wires 141, and the joint layers 113, 114 disposed between theconductive pattern 140 and at least one of the pair of glass plates 111,112. The thin conductive wire 141 of the conductive pattern 140 has thefirst surface 141 a facing one of the pair of glass plates 111, 112, andthe second surface 141 b facing the other of the pair of glass plates111, 112. When a width of the first surface 141 a of the thin conductivewire 141 is represented as W_(2a) (μm), a width of the second surface141 b of the thin conductive wire 14 is represented as W_(2b) (μm), anda cross-sectional area of the thin conductive wire 141 is represented asS_(2a) (μm²), the following relationships represented (a) and (b) aresatisfied.

0<IW _(2a) −W _(2b) I≦10  (a)

S _(2a)≧10  (b)

In addition, the aforementioned conductive pattern sheet 120 in thesecond embodiment includes the substrate 130, and the conductive patternsheet 140 disposed on the substrate 130 and including the thinconductive wires 141. The thin conductive wire 141 of the conductivepattern 140 has the proximal surface 141 b forming the surface on theside of the substrate 130, and the distal surface 141 a facing theproximal surface 141 b. When a width of the distal surface 141 a of thethin conductive wire 141 is represented as W_(2c) (μm), a width of theproximal surface 141 b of the thin conductive wire 141 is represented asW_(2d) (μm), and a cross-sectional area of the thin conductive wire 141is represented as S_(2b) (μm²), the following relationships represented(c) and (d) are satisfied.

0<IW _(2c) −W _(2d) I≦10  (c)

S _(2b)≧10  (d)

According to such a heating plate 110 and such a conductive patternsheet 120, it is possible to ensure a cross-sectional area sufficientfor obtaining a suitable conductivity, while reducing the maximum widthW (in the example shown in FIGS. 25 and 29, W_(2b), W_(2d)) of the thinconductive wire 141. Thus, a suitable conductivity of the conductivepattern 140 can be obtained, while the conductive pattern 140 can beeffectively made invisible.

The aforementioned second embodiment can be variously modified.Modification examples are described with reference suitably to thedrawings. In the below description and the drawings for the description,a component that can be similarly made as the above embodiment is shownby the same symbol as a component corresponding to the above embodiment,and overlapped description is omitted.

A modification examples of the manufacturing method of the heating plate110 are described with reference to FIGS. 36 to 40. FIGS. 36 to 40 aresectional views showing the modification example of the manufacturingmethod of the heating plate 110 in sequence.

Firstly, the conductive pattern sheet 120 is manufactured. Theconductive pattern sheet 120 may be manufactured by the method asdescribed above in the example of the manufacturing method of theheating plate 110.

Then, the glass plate 111, the joint layer 113 and the conductivepattern sheet 120 are superposed in this order, and heated/pressurized.In the example shown in FIG. 36, the joint layer 113 is provisionallyattached to the glass plate 111 firstly. Then, the glass plate 111 towhich the joint layer 113 has been provisionally attached is superposedfrom the side of the conductive pattern 140 of the conductive patternsheet 120 and heated/pressurized, in such a manner that the side of theglass plate 111, to which the joint layer 113 has been provisionallyattached, faces the conductive pattern sheet 120. Thus, as showing inFIG. 37, the glass plates 111 and the conductive pattern sheet 120 arejoined (provisionally joined or completely joined) through the jointlayer 113.

Then, as shown in FIG. 38, the substrate 130 of the conductive patternsheet 120 is removed. For example, when the holding layer 131 is formedto include a peeling layer, the substrate 130 of the conductive patternsheet 120 can be peeled from the conductive pattern 140 and the jointlayer 113 by means of the peeling layer.

The peeling layer may be, for example, a peeling layer of an interfacepeeling type, a peeling layer of an interlayer peeling type, a peelinglayer of a cohesion peeling type and so on. As a peeling layer of aninterface peeling type, there may be suitably used a peeling layerhaving relatively a lower adhesive property to the conductive pattern140 and the joint layer 113, than an adhesive property to the substrate130. Such a layer may be a silicone resin layer, a fluororesin layer, apolyolefin resin layer and so on. In addition, it is possible to use apeeling layer having relatively a lower adhesive property to thesubstrate 130, than an adhesive property to the conductive pattern 140and the joint layer 113. A peeling layer of an interlayer peeling typemay be, for example, a peeling layer including a plurality of filmlayers, and having relatively a lower adhesive property between theplurality of layers, than an adhesive property to the conductive pattern140, the joint layer 113 and the substrate 130. A peeling layer of acohesion peeling type may be, for example, a peeling layer formed bydispersing fillers as a dispersal phase in a base resin as a continuousphase.

When a peeling layer of an interface peeling type including a layerhaving relatively a lower adhesive property to the conductive pattern140 and the joint layer 113, than an adhesive property to the substrate130, is used, a peeling phenomenon occurs between the peeling layer, andthe conductive pattern 140 and the joint layer 113. In this case, it ispossible to make the peeling layer not remain on the conductive pattern140 and the joint layer 113. Namely, the substrate 130 is removedtogether with the peeling layer. When the substrate 130 and the peelinglayer are removed in this manner, the joint layer 113 is exposed intothe opening areas 144 of the conductive pattern 140.

On the other hand, when a peeling layer of an interface peeling typehaving relatively a lower adhesive property to the substrate 130, thanan adhesive property to the conductive pattern 140 and the joint layer113, is used, a peeling phenomenon occurs between the peeling layer andthe substrate 130. When a peeling layer of an interlayer peeling typeincluding a plurality of layers, and having relatively a lower adhesiveproperty between the plurality of film layers, than an adhesive propertyto the conductive pattern 140, the joint layer 113 and the substrate130, is used, a peeling phenomenon occurs between the plurality oflayers. When a peeling layer of a cohesion peeling type, which is formedby dispersing fillers as a dispersal phase in a base resin as acontinuous phase, is used, a peeling phenomenon occurs in the peelinglayer by cohesion failure.

Finally, the glass plate 111, the joint layer 113 and the conductivepattern 140, the joint layer 114, and the glass plate 112 are superposedin this order, and heated/pressurized. In the example shown in FIG. 39,the joint layer 114 is attached to the glass plate 112 firstly. Then,the glass plate 111, the conductive pattern 140 and the joint layer 113,and the glass plate 112 to which the joint layer 114 has beenprovisionally attached are superposed in this order andheated/pressurized, in such a manner that the side of the glass plate112, to which the joint layer 114 has been provisionally attached, facesthe conductive pattern 140 and the joint layer 113. Thus, the glassplate 111, the conductive pattern 140, the glass plates 112 are joined(completely joined) through the joint layers 113, 114, whereby theheating plate 110 shown in FIG. 40 is manufactured.

According to the heating plate 110 shown in FIG. 40, the heating plate110 can be free of substrate 130. Thus, the thickness of the heatingplate 110 as a whole can be reduced. In addition, the number of boundaryfaces in the heating plate 110 can be reduced. Thus, deterioration ofoptical properties, i.e., deterioration of visibility can be restrained.

Next, another modification example of the manufacturing method of theheating plate 110 is described with reference to FIGS. 41 and 42. FIGS.41 and 42 are sectional views showing the other modification example ofthe manufacturing method of the heating plate 110 in sequence.

Firstly, by the same steps as those of the above modification example ofthe manufacturing method of the heating plate 110, the glass plate 111and the conductive pattern sheet 120 are joined (provisionally joined)through the joint layer 113. Then, the substrate 130 is removedtherefrom. Namely, the laminate of the glass plate 111, the conductivepattern 140 and the joint layer 113 is obtained, which is described inthe above modification example of the manufacturing method of theheating plate 110 with reference to FIG. 38.

Then, as shown in FIG. 41, the glass plate 111, the joint layer 113 andthe conductive pattern 140, and the glass plate 112 are superposed inthis order, and heated/pressurized. Thus, the glass plate 111 and theconductive pattern 140 are joined (completely joined) through the jointlayer 113, and the glass plate 111 and 0 s the glass plate 112 arejoined (completely joined) through the joint layer 113. Thus, theheating plate 110 shown in FIG. 42 is manufactured.

According to the heating plate 10 shown in FIG. 42, the heating plate110 can be free of the substrate 130 and the joint layer 114. Thus, thethickness of the heating plate 110 as a whole can be further reduced. Inaddition, the number of boundary faces in the heating plate 110 can befurther reduced. Thus, deterioration of optical properties, i.e.,deterioration of visibility can be furthermore effectively restrained.Moreover, since the conductive pattern 140 and the glass plate 112 arein contact with each other, a heating efficiency of the glass plate 112by the conductive pattern 140 can be increased.

In the aforementioned second embodiment, the plurality of connectionelements 145 included in the conductive pattern 140 each have a linearshape (linear line segments) when viewed in the normal direction of theplate plane of the heating plate 110. However, not limited thereto, atleast some of the plurality of connection elements 145 may have a shapeother than a linear shape such as a curved shape or a polygonal lineshape. Specifically, the connection element 145 may have an arcuateshape, a parabolic shape, a corrugated shape, a zigzag shape, acombination shape of a curved line and a linear line, and so on. Inparticular, it is preferable that a rate of the connection elements 145which are straight lines (straight line segments) connecting the twobranch points 143, relative to the plurality of connection elements 145,is less than 20%. Namely, it is preferable that 80% or more of theconnection elements 145 have a shape other than a linear shape (straightline segment).

According to the conductive pattern 140 including the connectionelements 145 having a shape other than a linear shape (straight linesegment), light incident on the side surface of the connection element145 having a curved shape or a polygonal line shape and so on isreflected irregularly on the side surface. Thus, it can be restrainedthat the light incident on the side surface of the connection element145 from a certain direction (headlight of an oncoming automobile,sunlight and so on) is reflected on the side surface in a certaindirection correspondingly to the incident direction. Thus, it can berestrained that the reflected light is visible to an observer such as adriver, so that the conductive pattern 140 having the connectionelements 145 is visible to the observer. As a result, the deteriorationof visibility of an observer through a pane, which is caused by thevisible conductive pattern 140, can be restrained.

In the aforementioned second embodiment, the conductive pattern 140 hasa pattern determined based on the Voronoi diagram, i.e., a number of theopening areas 144 which have shapes which do not have a repeatedregularity (periodic regularity) and are arranged at pitches which donot have a repeated regularity (periodic regularity). However, notlimited to this pattern, there may be used, as the conductive pattern140, various patterns such as a pattern in which triangular,rectangular, or hexagonal opening areas of the same shape are regularlyarranged, a pattern in which opening areas of different shapes areregularly arranged, and so on.

The heating plate 110 may be used in a rear window, a side window and asun roof of the automobile 1. In addition, the heating plate 110 may beused in a window or a transparent part of a door of a vehicle other thanan automobile, such as a railway, an aircraft, a vessel, a space vesseland so on, or a window or a door of a building, and a window or atransparent part of a door of a refrigerator, an exhibition box and astorage or preservation installation such as a cabinet.

Further, in addition to a vehicle, the heating plate 110 may be used ina part by which an inside and an outside is partitioned, such as awindow of a building, a store and a house.

Although some modification examples of the above second embodiment aredescribed, the modification examples can be naturally combined with oneanother for application.

Third Embodiment

FIG. 1 and FIGS. 43 to 56 are views for explaining a third embodimentaccording to the present invention. In the third embodiment describedbelow, a component corresponding to that of the first and secondembodiments is shown by a symbol in 200 s with the same last two digits,and overlapped description is omitted.

FIG. 43 is a view of a heating plate when viewed in a normal directionof a plate plane thereof. FIG. 44 is a cross sectional view of theheating plate of FIG. 43. FIG. 45 is a view showing conditions ofrespective members constituting the heating plate of FIG. 44 before therespective members are laminated. The heating plate in this embodimentis sometimes referred to as “laminated glass”.

FIG. 43 shows a heating plate 210 when viewed in a normal direction of aplate plane thereof. FIG. 44 is a cross-sectional view corresponding toa XLIV-XLIV line of the heating plate 210 of FIG. 43. The heating plate210 includes a pair of curved glass plates 211, 212, a conductivepattern sheet (pattern sheet) 220 disposed between the pair of curvedglass plates 211, 212, a joint layer 213 that joins the glass plate 211and the conductive pattern sheet 220, and a joint layer 214 that joinsthe glass plate 212 and the conductive pattern sheet 220.

The conductive pattern sheet 220 includes a substrate 230, a conductivepattern 240 formed on the substrate 230, a wiring part 15 for poweringthe conductive pattern 240, and a connection part 16 connecting theconductive pattern 240 and the wiring part 15.

In the example shown in FIGS. 43 and 44, the conductive pattern 240 ispowered by a power source 7, such as a battery, through the wiring part15 and the connection part 16, so that the conductive pattern 240generates heat by means of resistance heat. The heat generated by theconductive pattern 240 is transmitted to the glass plates 211, 212through the joint layers 213, 214, so that the glass plates 211, 212 arewarmed up. Thus, dew drops on the glass plates 211, 212 can be removedso that the glass plates 211, 112 can be defogged. When there is snow orice on the glass plates 211, 212, the snow or ice can be unfrozen. Thus,an excellent field of view of a passenger can be ensured.

In order to manufacture the heating plate 210, as shown in FIG. 45, thecurved glass plate 211, the joint layer 213, the conductive patternsheet 220, the joint layer 214 and the curved glass plate 212 aresuperposed in this order, and heated/pressurized, so that the curvedglass plates 211, the conductive pattern sheet 220 and the curved glassplates 212 are joined by the joint layers 213, 214.

Particularly when used as a front window, the glass plate 211, 212preferably has a high visible light transmittance in order not to hindera field of view of a passenger. A material of such a glass plate 211,212 may be soda lime glass, blue plate glass and so on, for example. Theglass plate 211, 212 preferably has a transmittance of 90% or more in avisible light area. The visible light transmittance of the glass plate211, 212 is specified as follows. Transmittance of light withmeasurement wavelength range of from 380 nm to 780 nm is measured byusing a spectrophotometer (manufactured by Shimadzu Corporation,“UV-3100PC”, compliant with ES K 0115). The visible light transmittanceis an average value of the transmittances at the respective wavelengths.The visible light transmittance may be lowered by partially or totallycoloring the glass plate 211, 212, for example. In this case, directsunlight can be shielded and an inside of the automobile is less visiblefrom outside.

In addition, the glass plate 211, 212 preferably has a thickness of notless than 1 mm and not more than 5 mm. With such a thickness, the glassplate 211, 212 excellent in strength and optical properties can beobtained.

The glass plates 211, 212 and the conductive pattern sheet 220 arejoined to each other through the joint layers 213, 214, respectively. Assuch a joint layer 213, 214, a layer made of a material having variousadhesion properties or gluing (pressure sensitive adhesive) propertiescan be employed. In addition, the joint layer 213, 214 preferably has ahigh visible light transmittance. A typical joint layer may be a layermade of polyvinyl butyral (PVB), for example. The joint layer 213, 214preferably has a thickness of not less than 0.15 mm and not more than0.7 mm.

Not limited to the illustrated example, the heating plate 210 may beprovided with another function layer for exerting a specific function.In addition, one function layer may exert two or more functions.Alternatively, for example, a function may be given to at least one ofthe glass plate 211, 212 of the heating plate 210, the joint layer 213,214 thereof, and the substrate 230 of the conductive pattern sheet 220thereof, which is described later. The function that can be given toheating plate 210 may be an antireflection (AR) function, a hard coat(HC) function having an abrasion resistance, an infrared ray shield(reflection) function, an ultraviolet ray shield (reflection) function,a polarizing function, an antifouling function and so on, for example.

Next, the conductive pattern sheet 220 is described. The conductivepattern sheet 220 includes the substrate 230, the conductive pattern 240disposed on the substrate 230, the wiring part 15 for powering theconductive pattern 240, and the connection part 16 connecting theconductive pattern 240 and the wiring part 15. The conductive patternsheet 220 may have a planar dimension substantially the same as that ofthe glass plate 211, 212 so as to be placed all over the heating plate210. Alternatively, the conductive pattern sheet 220 may be placed overonly a part of the heating plate 210, such as a part in front of adriver's seat.

The substrate 230 functions as a substrate that supports the conductivepattern 240. The substrate 230 is an electrically insulating substratethat transmits light of a wavelength (380 nm to 780 nm) of a visiblelight wavelength band, which is generally recognized as transparent. Thesubstrate 230 contains a thermoplastic resin.

A thermoplastic resin contained as a main component in the substrate 230may be any thermoplastic resin as long as it transmits visible light.The thermoplastic resin may be an acryl resin made of, e.g., polymethylmethacrylate, a polyolefin resin made of e.g., polypropylene, apolyester resin made of, e.g., polyethylene terephthalate orpolyethylene naphthalate, a cellulose-based resin made of, e.g.,triacetyl cellulose (cellulose triacetate), polyvinyl chloride,polystyrene, a polycarbonate resin, an AS resin and so on, for example.In particular, an acryl resin and polyethylene terephthalate arepreferred because of their excellent optical properties and moldability.

In addition, in consideration of support property during manufacture andlight transmission of the conductive pattern 240, the substrate 230preferably has a thickness of not less than 0.02 mm and not more than0.20 mm.

The conductive pattern 240 is described with reference to FIGS. 46 to48. FIG. 46 is a plan view of the conductive pattern sheet 220 whenviewed in a normal direction of a sheet plane thereof, showing anexample of an arrangement pattern of the conductive pattern 240.

The conductive pattern 240 is powered by the power source 7, such as abattery, through the wiring part 15 and the connection part 16, so as togenerate heat by means of resistance heat. The heat is transmitted tothe glass plates 211, 212 through the joint layers 213, 214, so that theglass plates 211, 212 are warmed up.

The conductive pattern 240 shown in FIG. 46 includes a plurality of thinconductive wires 241 that are arranged in a line and space pattern.Namely, the conductive pattern 240 includes the plurality of thinconductive wires 241 arranged in one direction. Each thin conductivewire 241 extends in the other direction not in parallel with the onedirection, apart from another thin conductive wire 241 adjacent in theone direction. In the illustrated example, each thin conductive wire 241is apart from another thin conductive wire 241 and connects the pair ofconnection parts 16. Namely, in the illustrated example, the onedirection is an extension direction of the connection part 16, which isan up and down direction of the automobile 1. In addition, the otherdirection is a right and left direction of the automobile 1. Althougheach thin conductive wire 241 extends in the other direction in acorrugated pattern, the thin conductive wire 241 may extend in apolygonal line shape or in a linear shape.

Although not formed in the illustrated example, the conductive pattern240 may include a thin wire connecting adjacent thin conductive wires241, i.e., a connection line. In addition, in the illustrated example,each thin conductive wire 241 extends in the right and left direction ofthe automobile 1, which is the other direction, each thin conductivewire 241 may extend in the up and down direction of the automobile 1.

In this embodiment, a copper film is used as a material for constitutingsuch a conductive pattern 240. A copper film means an electrolyticcopper foil, a rolled copper foil, a copper film formed (deposited) by aspattering method, a vacuum deposition method and so on. Although thedetails are described later, the conductive pattern 240 is formed bypatterning a copper film by an etching process.

FIG. 47 is a sectional view corresponding to an A-A line of FIG. 46,showing an example of a sectional shape of the thin conductive wire. Theplurality of thin conductive wires 241 constituting the conductivepattern 240 are formed on the substrate 230. In the illustrated example,the thin conductive wire 241 has a surface 241 a on the side of thesubstrate 230, a surface 241 b on the side opposed to the substrate 230,and side surfaces 241 c, 241 d. The thin conductive wire 241 hassubstantially a rectangular section in general. In this embodiment, aline width W (herebelow simply as “width”) of the thin conductive wire241, i.e., the width W along the sheet plane of the substrate 230 is notless than 1 μm and not more than 20 μm, preferably not less than 2 μmand not more than 15 μm. Thus, the conductive pattern 240 is seentransparent in general, and has an excellent see-through property. Inaddition, a height (thickness) H of the thin conductive wire 241, i.e.,the height (thickness) H along the normal direction to the sheet planeof the substrate 230 is preferably not less than 1 and not more than 20μm, and more preferably not less than 1 μm and not more than 10 μm.Since the thin conductive wire 241 having such a height dimension, inaddition to the line width W, is sufficiently thin, the conductivepattern 240 can be effectively made invisible.

In FIG. 47, the symbol P represents a pitch between the adjacent thinconductive wires (distance between the adjacent thin conductive wires241) in the conductive pattern 240. The pitch P is not less than 0.3 mmand not more than 2 mm. The pitch may be not less than 0.3 mm and notmore than 7 mm.

In addition, the thin conductive wire 241 includes a first dark colorlayer 246 disposed on the substrate 230, a conductive metal layer 245disposed on the first dark color layer 246, and a second dark colorlayer 247 disposed on the conductive metal layer 245. In other words,the surface of the conductive metal layer 245 on the side of thesubstrate 230 is covered with the first dark color layer 246, and thesurface of the conductive metal layer 245 on the side opposed to thesubstrate 230 and both side surfaces thereof are covered with the seconddark color layer 247.

The conductive metal layer 245 made of a metal material has relatively ahigh reflectance. When light is reflected on the conductive metal layer245 forming the conductive metal wires 241 of the conductive pattern240, the reflected light may be visible, which hinders a field of viewof a passenger. In addition, when the conductive metal layer 245 isvisible from outside, design is sometimes impaired. Thus, the dark colorlayers 246, 247 are disposed at least a part of the surface of theconductive metal layer 245. The dark color layers 246, 247 are layerhaving a visible light reflectance that is lower than that of theconductive metal layer 245, and are black-colored dark color layers, forexample. Due to the dark color layers 246, 247, the conductive metallayer 245 becomes less visible, whereby an excellent field of view of apassenger can be ensured. In addition, impairment of design when seenfrom outside can be prevented. However, such dark color layers 246, 247may be omitted. In this case, the width W of the thin conductive wire241 is a width of the single conductive metal layer 245.

FIG. 48 is a sectional view corresponding to the A-A line of FIG. 46,showing another sectional shape of the conductive metal wire. In theillustrated example, the conductive metal wire 241 includes a surface241 a on the side of the substrate 230, a surface 241 b on the sideopposed to the substrate 230, and side surfaces 241 c, 241 d. Thesurface 241 a on the side of the substrate 230 and the surface 241 b onthe side opposed to the substrate 230 are in parallel. The side surface241 c forms a tapered surface that is tapered to come close to the sidesurface 241 d as a certain point in the side surface 241 c moves awayfrom the substrate 230 along the normal direction of the sheet plane ofthe conductive pattern sheet 220. The side surface 241 d also forms atapered surface that is tapered to come close to the side surface 241 cas a certain point in the side surface 241 d moves away from thesubstrate 230 along the normal direction of the sheet plane of theconductive pattern sheet 220. The thin conductive wire 241 hassubstantially a trapezoidal section in general. Namely, the width of thethin conductive wire 241 changes to narrow as a certain point in thethin conductive wire 241 moves away from the substrate 230 along thenormal direction of the conductive pattern sheet 220. In addition,similarly to the example shown in FIG. 47, the surface of the conductivemetal layer 245 on the side of the substrate 230 is covered with thefirst dark color layer 246, and the surface of the conductive metallayer 245 on the side opposed to the substrate 230 and both sidesurfaces thereof are covered with the second dark color layer 247.

FIG. 48 shows that the thin conductive wire 241 has substantially atrapezoidal section in general, and that the width of the thinconductive wire 241 changes to narrow as a certain point in the thinconductive wire 241 moves away from the substrate 230 along the normaldirection of the conductive pattern sheet 220. However, not limitedthereto, the side surfaces 241 c, 241 d may be formed of curved lines,or may be formed in a tier-like shape. In addition, the width of thethin conductive wire 241 may be partially wider as a certain point inthe thin conductive wire 241 moves away from the substrate 230 along thenormal direction of the conductive pattern sheet 220. Namely, when thesection of the thin conductive wire 241 is seen generally andcomprehensively, it is sufficient that the width of the conductive wire241 changes to narrow as a certain point in the thin conductive wire 241moves away from the substrate 230 along the normal direction of theconductive pattern sheet 220.

In the example shown in FIG. 48, since the width of the thin conductivewire 241 changes to narrow as a certain point in the thin conductivewire 241 moves away from the substrate 230 along the normal direction ofthe conductive pattern sheet 220, when the glass plates 211, 212, thejoint layers 213, 214 and the conductive pattern sheet 220 arelaminated, the conductive pattern 240 can be reliably embedded in thejoint layer 213, and bubbles in an interface between the conductivepattern 240 and the joint layer 213 can be restrained from remainingtherein.

Next, an example of a manufacturing method of the heating plate 210 isdescribed with reference to FIGS. 49 to 56. FIGS. 49 to 56 are sectionalviews showing the example of the manufacturing method of the heatingplate 210 in sequence, particularly views for explaining manufacture ofthe conductive pattern sheet 220 in detail. After the conductive patternsheet 220 is manufactured, the conductive pattern sheet 220 issandwiched between the glass plates 211, 212 so that the heating plate210 is manufactured.

In order to manufacture the conductive pattern sheet 220, as shown inFIG. 49, the substrate 230 is firstly prepared. The substrate 230 is anelectrically insulating substrate that transmits light of a wavelength(380 nm to 780 nm) of a visible light wavelength band, which isgenerally recognized as transparent. The substrate 230 contains athermoplastic resin.

Then, as shown in FIG. 50, the first dark color 246 is disposed on thesubstrate 230. For example, the first dark color layer 263 can bedisposed on the substrate 230 by a plating method including electrolyticplating and electroless plating, a spattering method, a vacuumdeposition method, an ion plating method, a PVD method and a CVD methodother than these methods, or a combination method of the two or moremethods. Various known materials may be used as material of the firstdark color layer 246. For example, the material may be copper nitride,copper oxide, nickel nitride and so on.

Then, as shown in FIG. 51, the conductive metal layer 245 is disposed onthe first dark color layer 246. The conductive metal layer 245 is alayer formed of a copper film. When an electrolytic copper foil or arolled copper foil is used to form the conductive metal layer 245, theconductive metal layer 245 is disposed on the first dark color layer 246through a two-pack mixture type urethane ester-based adhesive(illustration omitted), for example. When an electrolytic copper foil isused, an electrolytic copper foil of not more than 7 μm is preferablyused in order to make thin the thin conductive wire 241 as much aspossible. When a copper film formed by a spattering method or a vacuumvapor deposition method is used, the conductive metal layer 245 isdisposed by depositing a film on the first dark color layer 246 throughan adhesive primer (illustration omitted). When a copper film formed bya spattering method or a vacuum vapor deposition method is used as theconductive metal layer 245, an electrolytic plated layer may bedeposited on the copper film, so as to form the conductive metal layer245 including the copper film formed by a spattering method or a vacuumvapor deposition method, and the electrolytic plated layer. As a filmdeposition method for a copper film, a spattering method, a vacuum vapordeposition method, an ion plating method, a PVD method other than thesemethods or a combination method thereof may be employed. In addition, asdescribed above, a copper film may be formed by an electrolytic platingmethod. Moreover, it is possible to employ a method in which anelectrolytic plating method is combined to the above describedspattering method, the vacuum vapor deposition method, the ion platingmethod and so on.

Then, as shown in FIG. 52, the resist layer 248 is disposed on theconductive metal layer 245. The resist layer 248 is a resin layer havinga photosensitivity to light of a predetermined wavelength range, such asultraviolet light. The resin layer may be formed by adhering a resinfilm, or may be formed by applying a flowable resin. A concretephotosensitive property of the resist layer 248 is not specificallylimited. For example, a photo-curing type photosensitive material or aphoto-dissolving photosensitive material may be used as the resist layer248.

Thereafter, as shown in FIG. 53, the resist layer 248 is patterned toform the resist pattern 249. Various known methods may be used as themethod of patterning the resist layer 248. In this example, a resinlayer having a photosensitivity to light of a predetermined wavelengthrange, such as ultraviolet light, is used as the resist layer 248, and aknown photolithographic technique is used for patterning the resistlayer 248. Firstly, a mask which opens a part to be patterned or a maskwhich shields a part to be patterned is placed on the resist layer 248,and the resist layer 248 is irradiated with ultraviolet light throughthe mask. Thereafter, the part shielded by the mask from the ultravioletlight or the part irradiated with the ultraviolet light is removed bymeans of developing or the like. Thus, the patterned resist pattern 249can be formed. A laser patterning method without mask can be used.

Then, as shown in FIG. 54, the conductive metal layer 245 and the firstdark color layer 246 are etched with the resist pattern 249 serving as amask. Due to this etching process, the conductive metal layer 245 andthe first dark color layer 246 are patterned substantially similar tothe resist pattern 249. The etching method is not particularly limited,and a known method may be employed. The known method may be a wetetching method using etchant, a plasma etching method and so on.Thereafter, as shown in FIG. 55, the resist pattern 249 is removed.

Finally, the second dark color layer 247 is formed on the surface 241 bof the conductive metal layer 245 on the side opposed to the substrate230 and the side surfaces 241 c, 241 d. The second dark color layer 247is formed by, e.g., subjecting a part of a material constituting theconductive metal layer 245 to a darkening treatment (blackeningtreatment). Namely, in this case, the second dark color layer 247 madeof metallic oxide or metallic sulfide can be formed from the partconstituting the conductive metal layer 245. Alternatively, the seconddark color layer 247 as a coating film made of a dark color material ora plated layer made of nickel or chrome may be disposed on the surfaceof the conductive metal layer 245. In addition, the surface of theconductive metal layer 245 may be roughened, and the second dark colorlayer 247 may be disposed thereon.

In this example, the second dark color layer 247 is formed on thesurface 241 b of the conductive metal layer 245 on the side opposed tothe substrate 230 and the side surfaces 241 c, 241 d. However, notlimited thereto, the second dark color layer 247 may be formed only onthe surface 241 b of the conductive metal layer 245 on the side opposedto the substrate 230, or only on the side surfaces 241 c, 241 d of theconductive metal layer 245.

When the second dark color layer 247 is formed only on the surface 241 bof the conductive metal layer 245 on the side opposed to the substrate230, after the step shown in FIG. 51, for example, the second dark colorlayer 247 and the resist layer 248 are disposed in this order on theconductive metal layer 245, and the resist pattern 249 is formed bypatterning the resist layer 248. Thereafter, the second dark color layer247, the conductive metal layer 245 and the first dark color layer 246are etched with the resist pattern 249 serving as a mask.

Alternatively, when the second dark color layer 247 is formed only onthe side surfaces 241 c, 241 d of the conductive metal layer 245, afterthe step shown in FIG. 54, for example, the second dark color layer 247is formed without removing the resist pattern 249. After that, theresist pattern 249 is removed.

When the first dark color layer 246 is not necessary, the step ofdisposing the first dark color layer 246 on the substrate 230, which isshown in FIG. 50, is omitted.

Then, after the above conductive pattern sheet 220 is manufactured, thecurved glass plate 211, the joint layer 213, the conductive patternsheet 220, the joint layer 214 and the curved glass plate 212 aresuperposed in this order and heated/pressurized, whereby the heatingplate 210 is manufactured. The heating plate 210 includes the pair ofcurved glass plates 211, 212, the conductive pattern sheet 220 disposedbetween the pair of curved glass plates 211, 212, the joint layer 213disposed between the glass plate 211 and the conductive pattern sheet220 to join the glass plate 211 and the conductive pattern sheet 220,and the joint layer 214 disposed between the glass plate 212 and theconductive pattern sheet 220 to join the glass plate 212 and theconductive pattern sheet 220. The conductive pattern sheet 220 includesthe substrate 230 and the conductive pattern 240 formed on the substrate230. A desired pattern is easily given precisely to the conductivepattern 240 by the aforementioned patterning method. Since the pluralityof thin conductive wires 241 forming a pattern in the conductive pattern240 are disposed between the glass plates 211, 212, positions of thethin conductive wires 241 are fixed. Thus, a desired pattern of the thinconductive wires 241 can be easily given precisely to the heating plate210.

According to the heating plate 210 in the third embodiment, theconductive pattern 240 includes the plurality of thin conductive wires241 that are formed of a patterned copper film and arranged in the onedirection. Each thin conductive wire 241 extends in the other directionnot in parallel the one direction, apart from another thin conductivewire 241 adjacent in the one direction. To be more specific, theconductive pattern 240 includes the thin conductive wires 241 that arearrange in a line and space pattern. The line width of the thinconductive wire 241 is formed to be not less than 1 μm and not more than20 μm. In addition, the pitch between the adjacent thin conductive wires241 is formed to be not less than 0.3 mm and not more than 2 mm. Thus,since the thin conductive wire 241 is sufficiently thin, an excellentsee-through property can be obtained. In addition, a volume resistivityof the thin conductive wire 241 made of copper is low. Thus, althoughthe line width is thin, suitable heat generation can be obtained whenthe thin conductive wire 241 is powered. In this embodiment, theconductive pattern 240 is formed by patterning (through a step includingan etching process) a copper film. Thus, as described above, thisembodiment is advantageous in that a desired pattern of the thinconductive wires 241 can be easily given precisely to the heating plate210.

The aforementioned third embodiment may be variously modified.

For example, the conductive pattern 240 of the conductive pattern sheet220 may be provided, not on the surface of the substrate 230 on the sideof the joint layer 211, but on the surface on the side of the jointlayer 212. Alternatively, the conductive pattern 240 may be providedboth on the surfaces of the substrate 230 on the side of the joint layer211 and on the side of the joint layer 212.

The heating plate 210 may be used in a rear window, a side window and asun roof of the automobile 1. In addition, the heating plate 210 may beused in a window of a vehicle other than an automobile, such as arailway, an aircraft, a vessel, a space vessel and so on.

Further, in addition to a vehicle, the heating plate 210 may be used ina part by which an inside and an outside is partitioned, such as awindow of a building, a store and a house.

Although some modification examples of the above third embodiment aredescribed, the modification examples can be naturally combined with oneanother for application.

Examples Related to Third Embodiment

Although the third embodiment is described in more detail herebelow byusing examples, the third embodiment is not limited to these examples.In addition, a comparative example is also described.

Example 1

The heating plate 210 in Example 1 was manufactured as follows. As thesubstrate 230, there was firstly prepared a PET (polyethyleneterephthalate) film (manufactured by TOYOBO Co., Ltd A4300) having athickness of 100 μm, a width of 98 cm and a length of 100 m. A two-packmixture type urethane ester-based adhesive was applied to the substrate230 by a gravure coater, such that a thickness of the cured adhesivebecame 7 μm. Then, an electrolytic copper foil having a thickness of 10μm, a width of 97 cm and a length of 80 m was laminated as theconductive metal layer 245 on the substrate 230 through an adhesive. Theelectrolytic copper foil and the substrate 230 were maintained for 4days in an environment of 50° C., so that the electrolytic copper foilwas secured on the substrate 230.

Thereafter, the resist layer 248 was laminated on the electrolyticcopper foil (conductive metal layer 245), and was exposed in a line andspace pattern of 1.5 mm in pitch and 4 μm in line width. Then, anunnecessary resist was cleaned (removed) to form the resist pattern 249.The electrolytic copper foil was etched with the resist pattern 249serving as a mask. Then, after cleaning, there was obtained theconductive pattern sheet 220 with the conductive pattern 240 includingthe thin conductive wires 241 that were arranged in the line and spacepattern of 1.5 mm in pitch and 4 μm in line width.

Then, the thus obtained conductive pattern sheet 220 was cut to have anupper base of 125 cm, a lower base of 155 cm and a height of 96 cm.Then, the conductive pattern sheet 220 was disposed between the glassplates 211, 212 having a shape, when viewed in a normal direction, whichhas an upper base of 120 cm, a lower base of 150 cm and height of 95 cm,through the joint layers 213, 214 formed of PBV adhesive sheets havingthe same size as that of the glass plates 211, 212. Then, the laminateof these members was heated/pressurized (vacuum laminated). Then, thejoint layer and the conductive pattern sheet 220 projecting from betweenthe glass plates 211, 212 were trimmed so as to obtain the heating plate210 according to Example 1.

Upon inspection of the heating plate 210 according to Example 1 witheyes, the heating plate 210 was found to have an excellent see-throughproperty. In addition, light beam stripes were not conspicuous. Lightbeam stripes are visible stripes of light. When a heating wire (thinconductive wire) in a defroster apparatus is thick, light beam stripstend to be large and thus can be conspicuous. Since a resistance betweenthe wiring parts 15 was 0.7Ω, it was confirmed that suitable heatgeneration could be obtained when the heating plate 210 was powered. Theabove resistance between the wiring parts 15 was a resistance in a casewhere a current of 12V was applied.

Example 2

The heating plate 210 in Example 2 was manufactured as follows. As thesubstrate 230, there was firstly prepared a PET (polyethyleneterephthalate) film (manufactured by TOYOBO Co., Ltd A4300) having athickness of 100 μm, a width of 98 cm and a length of 100 m. Copper wasspattered to the substrate 330 though an adhesive primer such that thecopper had a thickness of 500 nm. Further, copper was laminated byplating on the spattered copper, so as to obtain a conductive metallayer (copper film) 345 formed of the spattered copper film and theplated copper, with a total thickness of 2 μm.

Thereafter, the resist layer 248 was laminated on the conductive metallayer 245, and was exposed in a line and space pattern of 0.3 mm inpitch and 2 μm in line width. Then, an unnecessary resist was cleaned(removed) to form the resist pattern 249. The copper film was etchedwith the resist pattern 249 serving as a mask. Then, after cleaning,there was obtained the conductive pattern sheet 220 with the conductivepattern 240 including the thin conductive wires 241 that were arrangedin the line and space pattern of 0.3 mm in pitch and 2 μm in line width.

Then, the thus obtained conductive pattern sheet 220 was cut to have anupper base of 125 cm, a lower base of 155 cm and a height of 96 cm.Then, the conductive pattern sheet 220 was disposed between the glassplates 211, 212 having a shape, when viewed in a normal direction, whichhas an upper base of 120 cm, a lower base of 150 cm and height of 95 cm,through the joint layers 213, 214 formed of PBV adhesive sheets havingthe same size as that of the glass plates 211, 212. Then, the laminateof these members was heated/pressurized (vacuum laminated). Then, thejoint layer and the conductive pattern sheet 220 projecting from betweenthe glass plates 211, 212 were trimmed so as to obtain the heating plate210 according to Example 2.

Upon inspection of the heating plate 210 according to Example 2 witheyes, the heating plate 210 was found to have an excellent see-throughproperty. In addition, light beam stripes were not conspicuous. Since aresistance between the wiring parts 15 was 1.3Ω, it was confirmed thatsuitable heat generation could be obtained when the heating plate 210was powered. The above resistance between the wiring parts 15 was aresistance in a case where a current of 12V was applied.

Example 3

In the manufacture of the heating plate 210 in Example 3, when theconductive pattern sheet 220 was manufactured, a copper foil having athickness of 6 μm was used. The resist layer 248 on the copper foil(conductive metal layer 245) was exposed in a line and space pattern of1 mm in pitch and 6 μm in line width. Other than that, by using the samematerials and the same steps as those of Example 1, the heating plate210 was obtained. The conductive pattern sheet 220 in the heating plate210 was provided with the conductive pattern 240 including the thinconductive wires 241 that were arranged in the line and space pattern of1 mm in pitch and 6 μm in line width. In the heating plate 210 inExample 3, since a resistance between the wiring parts 15 was 0.5Ω, itwas confirmed that suitable heat generation could be obtained when theheating plate 210 was powered. The above resistance between the wiringparts 15 was a resistance in a case where a current of 12V was applied.

Example 4

In the manufacture of the heating plate 210 in Example 4, when theconductive pattern sheet 220 was manufactured, a copper foil having athickness of 10 μm was used. The resist layer 248 on the copper foil(conductive metal layer 245) was exposed in a line and space pattern of1.7 mm in pitch and 8 μm in line width. Other than that, by using thesame materials and the same steps as those of Example 1, the heatingplate 210 was obtained. The conductive pattern sheet 220 in the heatingplate 210 was provided with the conductive pattern 240 including thethin conductive wires 241 that were arranged in the line and spacepattern of 1.7 mm in pitch and 8 μm in line width. In the heating plate210 in Example 4, since a resistance between the wiring parts 15 was0.4Ω, it was confirmed that suitable heat generation could be obtainedwhen the heating plate 210 was powered. The above resistance between thewiring parts 15 was a resistance in a case where a current of 12V wasapplied.

Example 5

In the manufacture of the heating plate 210 in Example 5, when theconductive pattern sheet 220 was manufactured, copper was spattered tohave a thickness of 1000 nm, and the conductive metal layer 245 (copperfilm) was laminated on the substrate 230 without plating copper. Theresist layer 248 on the conductive metal layer 245 was exposed in a lineand space pattern of 0.3 mm in pitch and 9 μm in line width. Other thanthat, by using the same materials and the same steps as those of Example2, the heating plate 210 was obtained. The conductive pattern sheet 220in the heating plate 210 was provided with the conductive pattern 240including the thin conductive wires 241 that were arranged in the lineand space pattern of 0.3 mm in pitch and 9 μm in line width. In theheating plate 210 in Example 5, since a resistance between the wiringparts 15 was 0.6Ω, it was confirmed that suitable heat generation couldbe obtained when the heating plate 210 was powered. The above resistancebetween the wiring parts 15 was a resistance in a case where a currentof 12V was applied.

Example 6

In the manufacture of the heating plate in Example 6, a copper foilhaving a thickness of 6 μm was used similarly to Example 3. The resistlayer 248 on the copper foil was exposed in a line and space pattern of0.4 mm in pitch and 1 μm in line width. Other than that, by using thesame materials and the same steps as those of Example 3, there wasobtained a heating plate with conductive pattern sheet including theconductive pattern having the thin conductive wires that were arrangedin the line and space pattern of 0.4 mm in pitch and 1 μm in line width.In the heating plate in Example 6, disconnection occurred in a lot oflocations, so that suitable heat generation was not obtained when theheating plate was powered. However, unless disconnection occurred, it isconsidered that an excellent see-through property can be obtained aswell as suitable heat generation can be obtained.

Example 7

In the manufacture of the heating plate in Example 7, a conductive metallayer, which included a spattered copper film and a plated copper, witha total thickness of 2 μm, was laminated on the substrate similarly toExample 2. The resist layer 248 on the conductive metal layer wasexposed in a line and space pattern of 1 mm in pitch and 15 μm in linewidth. Other than that, by the same steps as those of Example 2, therewas obtained a heating plate with a conductive pattern including thinconductive wires that were arranged in the line and space pattern of 1mm in pitch and 15 μm in line width. In the heating plate in Example 7,since copper wires were visible, an excellent see-through property couldnot be obtained. However, there could be obtained a see-through propertywhich did not hinder driving of an automobile, for example.

Comparative Example

In the manufacture of a heating plate in Comparative Example, a copperfoil having a thickness of 10 μm was used similarly to Example 4. Aresist layer on the copper foil was exposed in a line and space patternof 3 mm in pitch and 8 μm in line width. Other than that, by the samesteps as those of Example 4, there was obtained a heating plate with aconductive pattern including thin conductive wires that were arranged inthe line and space pattern of 3 mm in pitch and 8 μm in line width. Theheating plate in the Comparative Example had an excellent transparency.On the other hand, after being stored in a refrigerator, the heatingplate in the Comparative Example was taken out and powered. In thiscase, increase of temperature at an intermediate between copper wireswas slow, and it took more time that that of examples to defog theheating plate.

Fourth Embodiment

FIG. 1 and FIGS. 57 to 70 are views for explaining a fourth embodimentaccording to the present invention. In the fourth embodiment describedbelow, a component corresponding to that of the first and secondembodiments is shown by a symbol in 300 s with the same last two digits,and overlapped description is omitted.

FIG. 57 is a view of a heating plate when viewed in a normal directionof a plate plane thereof. FIG. 58 is a cross-sectional view of theheating plate of FIG. 57. FIG. 59 is a view showing conditions ofrespective member constituting the heating plate of FIG. 58 before therespective members are laminated. The heating plate in this embodimentis sometimes referred to as “laminated glass”.

FIG. 57 shows a heating plate 310 when viewed in a normal direction of aplate plane thereof. FIG. 58 is a cross-sectional view corresponding toa LVIII-LVIII line of the heating plate 310 of FIG. 57. The heatingplate 310 includes a pair of curved glass plates 311, 312, a conductivepattern sheet (pattern sheet) 320 disposed between the pair of curvedglass plates 311, 312, a joint layer 313 that joins the glass plate 311and the conductive pattern sheet 320, and a joint layer 314 that joinsthe glass plate 312 and the conductive pattern sheet 320.

The conductive pattern sheet 320 includes a substrate 330, a conductivepattern (conductive pattern member) 340 formed on the substrate 330, awiring part 15 for powering the conductive pattern 340, and a connectionpart 16 connecting the conductive pattern 340 and the wiring part 15.

In the example shown in FIGS. 57 and 58, the conductive pattern 340 ispowered by a power source 7, such as a battery, through the wiring part15 and the connection part 16, so that the conductive pattern 340generates heat by means of resistance heat. The heat generated by theconductive pattern 340 is transmitted to the glass plates 311, 312through the joint layers 313, 314, so that the glass plates 311, 312 arewarmed up. Thus, due drops on the glass plates 311, 312 can be removedso that the glass plates 311, 312 can be defogged. when there is snow orice on the glass plates 311, 312, the snow or ice can be unfrozen. Thus,an excellent filed of view of a passenger can be ensured.

In order to manufacture the heating plate 310, as shown in FIG. 59, thecurved glass plate 311, the joint layer 313, the conductive patternsheet 320, the joint layer 314 and the curved glass plate 312 aresuperposed in this order, and heated/pressurized, so that the curvedglass plate 311, the conductive pattern sheet 320 and the curved glassplates 312 are joined through the joint layers 313, 314.

Particularly when used as a front window, the glass plate 311, 312preferably has a high visible light transmittance in order not to hindera field of view of a passenger. A material of such a glass plate 311,312 may be soda lime glass, blue plate glass and so on, for example. Theglass plate 311, 312 preferably has a transmittance of 90% or more in avisible light area. The visible light transmittance of the glass plate311, 312 is specified as follows. Transmittance of light withmeasurement wavelength range of from 380 nm to 780 nm is measured byusing a spectrophotometer (manufactured by Shimadzu Corporation,“UV-3100PC”, compliant with JIS K 0115). The visible light transmittanceis an average value of the transmittances at the respective wavelengths.The visible light transmittance may be lowered by partially or totallycoloring the glass plate 311, 312, for example. In this case, directsunlight can be shielded and an inside of the automobile is less visiblefrom outside.

In addition, the glass plate 311, 312 preferably has a thickness of notless than 1 mm and not more than 5 mm. With such a thickness, the glassplate 311, 312 excellent in strength and optical properties can beobtained.

The glass plates 311, 312 and the conductive pattern sheet 320 arejoined to each other through the joint layers 313, 314, respectively. Assuch a joint layer 313, 314, a layer made of a material having variousadhesion properties or gluing (pressure sensitive adhesive) properties.In addition, the joint layer 313, 314 preferably has a high visiblelight transmittance. A typical joint layer may be a layer made ofpolyvinyl butyral (PVB), for example. The joint layer 313, 314preferably has a thickness of not less than 0.15 mm and not more than0.7 mm.

Not limited to the illustrated example, the heating plate 310 may beprovided with another function layer for exerting a specific function.In addition, one function layer may exert two or more functions.Alternatively, for example, a function may be given to at least one ofthe glass plate 311, 312 of the heating plate 310, the joint layer 313,314 thereof, and the substrate 330 of the conductive pattern sheet 320thereof, which is described later. The function that can be given toheating plate 310 may be an antireflection (AR) function, a hard coat(HC) function having an abrasion resistance, an infrared ray shield(reflection) function, an ultraviolet ray shield (reflection) function,a polarizing function, an antifouling function and so on, for example.

Next, the conductive pattern sheet 320 is described. The conductivepattern sheet 320 includes the substrate 330, the conductive pattern 340disposed on the substrate 330, the wiring part 15 for powering theconductive pattern 240, and the connection part 16 connecting theconductive pattern 340 and the wiring part 15. The conductive patternsheet 320 may have a planar dimension substantially the same as that ofthe glass plate 311, 312 so as to be placed all over the heating plate310. Alternatively, the conductive pattern sheet 320 may be placed overonly a part of the heating plate 310, such as a part in front of adriver's seat.

The substrate 330 functions as a substrate that supports the conductivepattern 340. The substrate 330 is an electrically insulating substratethat transmits light of a wavelength (380 nm to 780 nm) of a visiblelight wavelength band, which is generally recognized as transparent. Thesubstrate 330 contains a thermoplastic resin.

A thermoplastic resin contained as a main component in the substrate 330may be any thermoplastic resin as long as it transmits visible light.The thermoplastic resin may be an acryl resin made of, e.g., polymethylmethacrylate, a polyolefin resin made of e.g., polypropylene, apolyester resin made of, e.g., polyethylene terephthalate orpolyethylene naphthalate, a cellulose-based resin made of, e.g.,triacetyl cellulose (cellulose triacetate), polyvinyl chloride,polystyrene, a polycarbonate resin, an AS resin and so on, for example.In particular, an acryl resin and polyethylene terephthalate arepreferred because of their excellent optical properties and moldability.

In addition, in consideration of support property during manufacture andlight transmission of the conductive pattern 340, the substrate 330preferably has a thickness of not less than 0.02 mm and not more than0.20 mm.

The conductive pattern 340 is described with reference to FIGS. 60 to62. FIG. 60 is a plan view of the conductive pattern sheet 320 whenviewed in a normal direction of a sheet plane thereof, showing anexample of an arrangement pattern of the conductive pattern 340.

The conductive pattern 340 is powered by the power source 7, such as abattery, through the wiring part 15 and the connection part 16, so as togenerate heat by means of resistance heat. The heat is transmitted tothe glass plate 311, 312 through the joint layers 313, 314, so that theglass plates 311, 312 are warmed up.

The conductive pattern 340 shown in FIG. 60 is a member including thinconductive wires 341 that are arranged in a mesh pattern defining anumber of openings 343. The conductive pattern 340 is a member that isalso referred to as conductive mesh. The conductive pattern 340 includesa plurality of connection elements 344 that extend between two branchpoints 342 to define the openings 343. Namely, the thin conductive wires341 are an aggregation of a number of the connection elements 344 eachforming the branch points 342 at both ends thereof. Particularly in theillustrated example, the three connection elements 344 are connected atequal angles at each branch point 342, so that there are defined anumber of the openings 343 of the same honeycomb shape (hexagonal shape)each of which is surrounded by the six connection elements 344.

In the illustrated example, the conductive pattern 340 includes the thinconductive wires 341 that are arranged in a mesh pattern in which theopenings 343 of the same honeycomb shape are regularly defined. However,not limited to the mesh pattern, the conductive pattern 340 may have thethin conductive wires 341 that are arranged in various mesh patternssuch as in a mesh pattern (grid pattern) in which the openings 343 ofthe same shape such as a triangular shape or a rectangular shape areregularly defined, a mesh pattern in which the openings 343 of differentshapes are regularly defined, a mesh pattern in which the openings 343of different shapes are irregularly defined, such as a Voronoi meshpattern, and so on. In the case of a honeycomb pattern, current can besmoothly branched at the branch point 342 into two directions to changetraveling directions. Thus, since current easily flows throughout theconductive pattern 340, uniform heat generation occurs in the conductivepattern 340 as a whole, to thereby improve a see-through property.

In this embodiment, a copper film is used as a material for constitutingsuch a conductive pattern 240. A copper film means an electrolyticcopper foil, a rolled copper foil, a copper film formed (deposited) by aspattering method, a vacuum deposition method and so on. Although thedetails are described later, the conductive pattern 340 is formed bypatterning a copper film by an etching process.

FIG. 61 is a sectional view corresponding to an A-A line of FIG. 60,showing an example of a sectional shape of the thin conductive wire. Thethin conductive wires 341 (connection elements 344) constituting theconductive pattern 340 are formed on the substrate 330. In theillustrated example, the thin conductive wire 341 has a surface 341 a onthe side of the substrate 330, a surface 341 b on the side opposed tothe substrate 330, and side surfaces 341 c, 341 d. The thin conductivewire 341 has substantially a rectangular section in general. In thisembodiment, a line width W (herebelow simply as “width”) of the thinconductive wire 341, i.e., the width W along the sheet plane of thesubstrate 330 is not less than 1 μm and not more than 20 μm, preferablynot less than 2 μm and not more than 15 μm. Thus, the conductive pattern340 is seen transparent in general, and has an excellent see-throughproperty. In addition, a height (thickness) H of the thin conductivewire 341, i.e., the height (thickness) H along the normal direction tothe sheet plane of the substrate 330 is preferably not less than 1 μMand not more than 20 μm, and more preferably not less than 1 μm and notmore than 10 μm. Since the thin conductive wire 341 having such a heightdimension, in addition to the line width W, is sufficiently thin, theconductive pattern 340 can be effectively made invisible.

In FIG. 61, the symbol P represents a pitch between the adjacentopenings 343 (distance between centers of the adjacent openings 343) inthe honeycomb pattern of the conductive pattern 340 when it has ahoneycomb pattern. The pitch P is preferably not less than 0.3 mm andnot more than 7.0 mm, and more preferably not less than 0.3 mm and notmore than 2 mm. When the conductive pattern 340 has a grid pattern, apitch between adjacent rectangular openings in the grid pattern ispreferably not less than 0.3 mm and not more than 7.0 mm, and morepreferably not less than 0.3 mm and not more than 2 mm.

In addition, the thin conductive wire 341 includes a first dark colorlayer 346 disposed on the substrate 330, a conductive metal layer 345disposed on the first dark color layer 346, and a second dark colorlayer 347 disposed on the conductive metal layer 345. In other words,the surface of the conductive metal layer 345 on the side of thesubstrate 330 is covered with the first dark color layer 346, and thesurface of the conductive metal layer 345 on the side opposed to thesubstrate 330 and both side surfaces thereof are covered with the seconddark color layer 347.

The conductive metal layer 345 made of a metal material has relatively ahigh reflectance. When light is reflected on the conductive metal layer345 forming the conductive metal wires 341 of the conductive pattern340, the reflected light may be visible, which hinders a field of viewof a passenger. In addition, when the conductive metal layer 345 isvisible from outside, design is sometimes impaired. Thus, the dark colorlayers 346, 347 are disposed at least a part of the surface of theconductive metal layer 345. The dark color layers 346, 347 are layerhaving a visible light reflectance that is lower than that of theconductive metal layer 345, and are black-colored dark color layers, forexample. Due to the dark color layers 346, 347, the conductive metallayer 345 becomes less visible, whereby an excellent field of view of apassenger can be ensured. In addition, impairment of design when seenfrom outside can be prevented. However, such dark color layers 346, 347may be omitted. In this case, the width W of the thin conductive wire341 is a width of the single conductive metal layer 345.

FIG. 62 is a sectional view corresponding to the A-A line of FIG. 60,showing another sectional shape of the thin conductive wire. In theillustrated example, the thin conductive wire 341 (connection element344) includes a surface 341 a on the side of the substrate 330, asurface 341 b on the side opposed to the substrate 330, and sidesurfaces 341 c, 341 d. The surface 341 a on the side of the substrate330 and the surface 341 b on the side opposed to the substrate 330 arein parallel. The side surface 341 c forms a tapered surface that istapered to come close to the side surface 341 d as a certain point inthe side surface 341 c moves away from the substrate 330 along thenormal direction of the sheet plane of the conductive pattern sheet 320.The side surface 341 d also forms a tapered surface that is tapered tocome close to the side surface 341 c as a certain point in the sidesurface 341 d moves away from the substrate 330 along the normaldirection of the sheet plane of the conductive pattern sheet 320. Thethin conductive wire 341 has substantially a trapezoidal section ingeneral. Namely, the width of the thin conductive wire 341 changes tonarrow as a certain point in the thin conductive wire 341 moves awayfrom the substrate 330 along the normal direction of the conductivepattern sheet 320. In addition, similarly to the example shown in FIG.61, the surface of the conductive metal layer 345 on the side of thesubstrate 330 is covered with the first dark color layer 346, and thesurface of the conductive metal layer 345 on the side opposed to thesubstrate 330 and both side surfaces thereof are covered with the seconddark color layer 347.

FIG. 62 shows that the thin conductive wire 341 has substantially atrapezoidal section in general, and that the width of the thinconductive wire 341 changes to narrow as a certain point in the thinconductive wire 341 moves away from the substrate 330 along the normaldirection of the conductive pattern sheet 320. However, not limitedthereto, the side surfaces 341 c, 341 d may be formed of curved lines,or may be formed in a tier-like shape. In addition, the width of thethin conductive wire 341 may be partially wider as a certain point inthe thin conductive wire 341 moves away from the substrate 330 along thenormal direction of the conductive pattern sheet 320. Namely, when thesection of the thin conductive wire 341 is seen generally andcomprehensively, it is sufficient that the width of the conductive wire341 changes to narrow as a certain point in the thin conductive wire 341moves away from the substrate 330 along the normal direction of theconductive pattern sheet 320.

In the example shown in FIG. 62, since the width of the thin conductivewire 341 changes to narrow as a certain point in the thin conductivewire 341 moves away from the substrate 330 along the normal direction ofthe conductive pattern sheet 320, when the glass plates 311, 312, thejoint layers 313, 314 and the conductive pattern sheet 320 arelaminated, the conductive pattern 340 can be reliably embedded in thejoint layer 313, and bubbles in an interface between the conductivepattern 340 and the joint layer 313 can be restrained from remainingtherein.

Next, an example of a manufacturing method of the heating plate 310 isdescribed with reference to FIGS. 63 to 70. FIGS. 63 to 70 are sectionalviews showing the example of the manufacturing method of the heatingplate 310 in sequence, particularly views for explaining manufacture ofthe conductive pattern sheet 320 in detail. After the conductive patternsheet 320 is manufactured, the conductive pattern sheet 320 issandwiched between the glass plates 311, 312 so that the heating plate310 is manufactured.

In order to manufacture the conductive pattern sheet 320, as shown inFIG. 63, the substrate 330 is firstly prepared. The substrate 330 is anelectrically insulating substrate that transmits light of a wavelength(380 nm to 780 nm) of a visible light wavelength band, which isgenerally recognized as transparent. The substrate 330 contains athermoplastic resin.

Then, as shown in FIG. 64, the first dark color 346 is disposed on thesubstrate 330. For example, the first dark color layer 363 can bedisposed on the substrate 330 by a plating method including electrolyticplating and electroless plating, a spattering method, a vacuumdeposition method, an ion plating method, a PVD method and a CVD methodother than these methods, or a combination method of the two or moremethods. Various known materials may be used as material of the firstdark color layer 346. For example, the material may be copper nitride,copper oxide, nickel nitride and so on.

Then, as shown in FIG. 65, the conductive metal layer 345 is disposed onthe first dark color layer 346. The conductive metal layer 345 is alayer formed of a copper film. When an electrolytic copper foil or arolled copper foil is used to form the conductive metal layer 345, theconductive metal layer 345 is disposed on the first dark color layer 346through a two-pack mixture type urethane ester-based adhesive(illustration omitted), for example. When an electrolytic copper foil isused, an electrolytic copper foil of not more than 7 μm is preferablyused in order to make thin the thin conductive wire 341 as much aspossible. When a copper film formed by a spattering method or a vacuumvapor deposition method is used for forming the conductive metal layer345, the conductive metal layer 345 is disposed by depositing a film onthe first dark color layer 346 through an adhesive primer (illustrationomitted). When a copper film formed by a spattering method or a vacuumvapor deposition method is used as the conductive metal layer 345, anelectrolytic plated layer may be deposited on the copper film, so as toform the conductive metal layer 345 including the copper film formed bya spattering method or a vacuum vapor deposition method, and theelectrolytic plated layer. As a film deposition method for a copperfilm, a spattering method, a vacuum vapor deposition method, an ionplating method, a PVD method other than these methods or a combinationmethod thereof may be employed. In addition, as described above, acopper film may be formed by an electrolytic plating method. Moreover,it is possible to employ a method in which an electrolytic platingmethod is combined to the above described spattering method, the vacuumvapor deposition method, the ion plating method and so on.

Then, as shown in FIG. 66, the resist layer 348 is disposed on theconductive metal layer 345. The resist layer 348 is a resin layer havinga photosensitivity to light of a predetermined wavelength range, such asultraviolet light. The resin layer may be formed by adhering a resinfilm, or may be formed by applying a flowable resin. A concretephotosensitive property of the resist layer 348 is not specificallylimited. For example, a photo-curing type photosensitive material or aphoto-dissolving photosensitive material may be used as the resist layer348.

Thereafter, as shown in FIG. 67, the resist layer 348 is patterned toform the resist pattern 349. Various known methods may be used as themethod of patterning the resist pattern 349. In this example, a resinlayer having a photosensitivity to light of a predetermined wavelengthrange, such as ultraviolet light, is used as the resist layer 348, and aknown photolithographic technique is used for patterning the resistlayer 348. Firstly, a mask which opens a part to be patterned or a maskwhich shields a part to be patterned is placed on the resist layer 348,and the resist layer 348 is irradiated with ultraviolet light throughthe mask. Thereafter, the part shielded by the mask from the ultravioletlight or the part irradiated with the ultraviolet light is removed bymeans of developing or the like. Thus, the patterned resist pattern 349can be formed. A laser patterning method without mask can be used.

Then, as shown in FIG. 68, the conductive metal layer 345 and the firstdark color layer 346 are etched with the resist pattern 349 serving as amask. Due to this etching process, the conductive metal layer 345 andthe first dark color layer 346 are patterned substantially similar tothe resist pattern 349. The etching method is not particularly limited,and a known method may be employed. The known method may be a wetetching method using etchant, a plasma etching method and so on.Thereafter, as shown in FIG. 69, the resist pattern 349 is removed.

Finally, the second dark color layer 347 is formed on the surface 341 bof the conductive metal layer 345 on the side opposed to the substrate330 and the side surfaces 341 c, 341 d. The second dark color layer 347is formed by, e.g., subjecting a part of a material constituting theconductive metal layer 345 to a darkening treatment (blackeningtreatment). Namely, in this case, the second dark color layer 347 madeof metallic oxide or metallic sulfide can be formed from the partconstituting the conductive metal layer 345. Alternatively, the seconddark color layer 347 as a coating film made of a dark color material ora plated layer made of nickel or chrome may be disposed on the surfaceof the conductive metal layer 345. In addition, the surface of theconductive metal layer 345 may be roughened, and the second dark colorlayer 347 may be disposed thereon.

In this example, the second dark color layer 347 is formed on thesurface 341 b of the conductive metal layer 345 on the side opposed tothe substrate 330 and the side surfaces 341 c, 341 d. However, notlimited thereto, the second dark color layer 347 may be formed only onthe surface 341 b of the conductive metal layer 345 on the side opposedto the substrate 330, or only on the side surfaces 341 c, 341 d of theconductive metal layer 345.

When the second dark color layer 347 is formed only on the surface 341 bof the conductive metal layer 345 on the side opposed to the substrate330, after the step shown in FIG. 65, for example, the second dark colorlayer 347 and the resist layer 348 are disposed in this order on theconductive metal layer 345, and the resist pattern 349 is formed bypatterning the resist layer 348. Thereafter, the second dark color layer347, the conductive metal layer 345 and the first dark color layer 346are etched with the resist pattern 349 serving as a mask.

Alternatively, when the second dark color layer 347 is formed only onthe side surfaces 341 c, 341 d of the conductive metal layer 345, afterthe step shown in FIG. 68, for example, the second dark color layer 347is formed without removing the resist pattern 349. After that, theresist pattern 349 is removed.

When the first dark color layer 346 is not necessary, the step ofdisposing the first dark color layer 346 on the substrate 330, which isshown in FIG. 64, is omitted.

Then, after the above conductive pattern sheet 320 is manufactured, thecurved glass plate 311, the joint layer 313, the conductive patternsheet 320, the joint layer 314 and the curved glass plate 312 aresuperposed in this order and heated/pressurized, so that the heatingplate 310 is manufactured. The heating plate 310 includes the pair ofcurved glass plates 311, 312, the conductive pattern sheet 320 disposedbetween the pair of curved glass plates 311, 312, the joint layer 313disposed between the glass plate 311 and the conductive pattern sheet320 to join the glass plate 311 and the conductive pattern sheet 320,and the joint layer 314 disposed between the glass plate 312 and theconductive pattern sheet 320 to join the glass plate 312 and theconductive pattern sheet 320. The conductive pattern sheet 320 includesthe substrate 330 and the conductive pattern 340 formed on the substrate330. A desired pattern is easily given precisely to the conductivepattern 340 by the aforementioned patterning method. Thus, it ispossible to manufacture the heating plate 310 having an excellentoptical property.

According to the heating plate 310 in the fourth embodiment, theconductive pattern 340 includes the thin conductive wires 341 formed ofa patterned copper film and arranged in a mesh pattern. The line widthof the thin conductive wire 341 is formed to be not less than 1 μm andnot more than 20 μm. Thus, since the thin conductive wire 341 issufficiently thin, an excellent see-through property can be obtained. Inaddition, a volume resistivity of the thin conductive wire 341 made ofcopper is low. Thus, although the line width is thin, suitable heatgeneration can be obtained when the thin conductive wire 341 is powered.

The aforementioned fourth embodiment may be variously modified.

For example, the conductive pattern 340 of the conductive pattern sheet320 may be provided, not on the surface of the substrate 330 on the sideof the glass plate 311, but on the surface on the side of the glassplate 312. Alternatively, the conductive pattern 340 may be providedboth on the surfaces of the substrate 330 on the side of the glass plate311 and on the side of the glass plate 312.

The heating plate 310 may be used in a rear window, a side window and asun roof of the automobile 1. In addition, the heating plate 310 may beused in a window of a vehicle other than an automobile, such as arailway, an aircraft, a vessel, a space vessel and so on.

Further, in addition to a vehicle, the heating plate 310 may be used ina part by which an inside and an outside is partitioned, such as awindow of a building, a store and a house.

Although some modification examples of the above fourth embodiment aredescribed, the modification examples can be naturally combined with oneanother for application.

Examples Related to Fourth Embodiment

Although the fourth embodiment is described in more detail herebelow byusing examples, the fourth embodiment is not limited to these examples.

Example 1

The heating plate 310 in Expel 1 was manufactured as follows. As thesubstrate 330, there was firstly prepared a PET (polyethyleneterephthalate) film (manufactured by TOYOBO Co., Ltd A4300) having athickness of 100 μm, a width of 98 cm and a length of 100 m. A two-packmixture type urethane ester-based adhesive was applied to the substrate330 by a gravure coater, such that a thickness of the cured adhesivebecame 7 μm. Then, an electrolytic copper foil having a thickness of 10μm, a width of 97 cm and a length of 80 m was laminated as theconductive metal layer 345 on the substrate 330 through an adhesive. Theelectrolytic copper foil and the substrate 330 were maintained for 4days in an environment of 50° C., so that the electrolytic copper foilwas secured on the substrate 330.

Thereafter, the resist layer 348 was laminated on the electrolyticcopper foil (conductive metal layer 345), and was exposed in a gridpattern of 1.5 mm in pitch and 4 μm in line width. Then, an unnecessaryresist was cleaned (removed) to form the resist pattern 349. Theelectrolytic copper foil was etched with the resist pattern 349 servingas a mask. Then, after cleaning, there was obtained the conductivepattern sheet 320 with the conductive pattern 340 including the thinconductive wires 341 that were arranged in the grid pattern. In theconductive pattern sheet 320, a pitch of openings in the grid patternwas 1.5 mm, and a line width of the thin conductive wire 341 was 4 μm.

Then, the thus obtained conductive pattern sheet 320 was cut to have anupper base of 125 cm, a lower base of 155 cm and a height of 96 cm.Then, the conductive pattern sheet 320 was disposed between the glassplates 311, 312 having a shape, when viewed in a normal direction, whichhas an upper base of 120 cm, a lower base of 150 cm and height of 95 cm,through the joint layers 313, 314 formed of PBV adhesive sheets havingthe same size as that of the glass plates 311, 312. Then, the laminateof these members was heated/pressurized (vacuum laminated). Then, thejoint layer and the conductive pattern sheet 320 projecting from betweenthe glass plates 311, 312 were trimmed so as to obtain the heating plate310 according to Example 1.

Upon inspection of the heating plate 310 according to Example 1 witheyes, the heating plate 310 was found to have an excellent see-throughproperty. In addition, light beam stripes were not conspicuous. Lightbeam stripes are visible stripes of light. When a heating wire (thinconductive wire) in a defroster apparatus is thick, light beam stripstend to be large and thus can be conspicuous. Since a resistance betweenthe wiring parts 15 was 0.7Ω, it was confirmed that suitable heatgeneration could be obtained when the heating plate 310 was powered. Theabove resistance between the wiring parts 15 was a resistance in a casewhere a current of 12V was applied.

Example 2

The heating plate 310 in Example 2 was manufactured as follows. As thesubstrate 330, there was firstly prepared a PET (polyethyleneterephthalate) film (manufactured by TOYOBO Co., Ltd A4300) having athickness of 100 μm, a width of 98 cm and a length of 100 m. Copper wasspattered to the substrate 330 though an adhesive primer such that thecopper had a thickness of 500 nm. Further, copper was laminated byplating on the spattered copper, so as to obtain a conductive metallayer (copper film) 345 formed of the spattered copper film and theplated copper, with a total thickness of 2 μm.

Thereafter, the resist layer 348 was laminated on the conductive metallayer 345, and was exposed in a grid pattern of 0.3 mm in pitch and 3 μmin line width. Then, an unnecessary resist was cleaned (removed) to formthe resist pattern 349. The copper film was etched with the resistpattern 349 serving as a mask. Then, after cleaning, there was obtainedthe conductive pattern sheet 320 with the conductive pattern 340including the thin conductive wires 341 that were arranged in the gridpattern. In the conductive pattern sheet 320, a pitch of openings in thegrid pattern was 0.3 mm, and a line width of the thin conductive wire341 was 3 μm.

Then, the thus obtained conductive pattern sheet 320 was cut to have anupper base of 125 cm, a lower base of 155 cm and a height of 96 cm.Then, the conductive pattern sheet 320 was disposed between the glassplates 311, 312 having a shape, when viewed in a normal direction, whichhas an upper base of 120 cm, a lower base of 150 cm and height of 95 cm,through the joint layers 313, 314 formed of PBV adhesive sheets havingthe same size as that of the glass plates 311, 312. Then, the laminateof these members was heated/pressurized (vacuum laminated). Then, thejoint layer and the conductive pattern sheet 320 projecting from betweenthe glass plates 311, 312 were trimmed so as to obtain the heating plate310 according to Example 2.

Upon inspection of the heating plate 310 according to Example 2 witheyes, the heating plate 310 was found to have an excellent see-throughproperty. In addition, light beam stripes were not conspicuous. Since aresistance between the wiring parts 15 was 0.9Ω, it was confirmed thatsuitable heat generation could be obtained when the heating plate 310was powered. The above resistance between the wiring parts 15 was aresistance in a case where a current of 12V was applied.

Example 3

In the manufacture of the heating plate 310 in Example 3, when theconductive pattern sheet 320 was manufactured, a copper foil having athickness of 6 μm was used. The resist layer 348 on the copper foil(conductive metal layer 345) was exposed in a grid pattern of 1 mm inpitch and 6 μm in line width. Other than that, by using the samematerials and the same steps as those of Example 1, the heating plate310 was obtained. In the conductive pattern sheet 320 of the heatingplate 310, a pitch of openings in the grid pattern was 1 mm, and a linewidth of the thin conductive wire 341 was 6 μm. In the heating plate 310in Example 3, since a resistance between the wiring parts 15 was 0.5Ω,it was confirmed that suitable heat generation could be obtained whenthe heating plate 310 was powered. The above resistance between thewiring parts 15 was a resistance in a case where a current of 12V wasapplied.

Example 4

In the manufacture of the heating plate 310 in Example 4, when theconductive pattern sheet 320 was manufactured, a copper foil having athickness of 10 μm was used. The resist layer 348 on the copper foil(conductive metal layer 345) was exposed in a grid pattern of 1.7 mm inpitch and 8 μm in line width. Other than that, by using the samematerials and the same steps as those of Example 1, the heating plate310 was obtained. In the conductive pattern sheet 320 of the heatingplate 310, a pitch of openings in the grid pattern was 1.7 mm, and aline width of the thin conductive wire 341 was 8 μm. In the heatingplate 310 in Example 4, since a resistance between the wiring parts 15was 0.4Ω, it was confirmed that suitable heat generation could beobtained when the heating plate 310 was powered. The above resistancebetween the wiring parts 15 was a resistance in a case where a currentof 12V was applied.

Example 5

In the manufacture of the heating plate 310 in Example 5, when theconductive pattern sheet 320 was manufactured, copper was spattered tohave a thickness of 1000 nm, and the conductive metal layer 345 (copperfilm) was laminated on the substrate 330 without plating copper. Theconductive metal layer 345 was exposed in a grid pattern of 0.3 mm inpitch and 9 μm in line width. Other than that, by using the samematerials and the same steps as those of Example 2, the heating plate310 was obtained. In the conductive pattern sheet 320 of the heatingplate 310, a pitch of openings in the grid pattern was 0.3 mm, and aline width of the thin conductive wire 341 was 9 μm. In the heatingplate 310 in Example 5, since a resistance between the wiring parts 15was 0.6Ω, it was confirmed that suitable heat generation could beobtained when the heating plate 310 was powered. The above resistancebetween the wiring parts 15 was a resistance in a case where a currentof 12V was applied.

The below Table 1 shows a line width of the thin conductive wire 341, athickness of a copper film forming the thin conductive wire 341, a pitchof openings in the grid pattern, a measured resistance, a voltageapplied upon measurement and a heating value upon application of thevoltage, of the respective Examples 1 to 5. In Examples 1 to 5, asuitable heat value of from 150 to 310 W could be obtained.

TABLE 1 Line Applied Heating Width Thickness Pitch Resistance VoltageValue [μm] [μm] [mm] [Ω] [V] [W] Ex. 1 4 10 1.5 0.7 12 170 Ex. 2 3 2 0.30.9 12 150 Ex. 3 6 6 1 0.5 12 240 Ex. 4 8 10 1.7 0.4 12 310 Ex. 5 9 10.3 0.6 12 190

Fifth Embodiment

FIG. 1 and FIGS. 71 to 86 are views for explaining a fifth embodimentaccording to the present invention. In the fifth embodiment describedbelow, a component corresponding to that of the first to fourthembodiments is shown by a symbol in 400 s with the same last two digits,and overlapped description is omitted.

FIG. 71 is a view of a heating plate when viewed in a normal directionof a plate plane thereof. FIG. 72 is a cross-sectional view of theheating plate of FIG. 71. FIG. 73 is a view showing conditions ofrespective member constituting the heating plate of FIG. 72 before therespective members are laminated. The heating plate in this embodimentis sometimes referred to as “laminated glass”.

FIG. 71 shows a heating plate 410 when viewed in a normal direction of aplate plane thereof. FIG. 72 is a cross-sectional view corresponding toa LXXII-LXXII line of the heating plate 410 of FIG. 71. In the exampleshown in FIG. 72, a first glass plate 411, a first joint layer 413, aconductive pattern sheet (pattern sheet) 420, a second joint layer 414and the second glass plate 412 are laminated in this order to form theheating plate 410. The conductive pattern sheet 420 includes a substrate430, and a conductive pattern (conductive pattern member) 440 disposedon the substrate 430. The conductive pattern 440 includes thinconductive wires 441 that are arranged in a pattern. As shown in FIG.74, in this embodiment, the thin conductive wires 441 are arranged in amesh pattern, which is described in more detail below.

In addition, as described in FIG. 71, the heating plate 410 includes awiring part 15 for powering the conductive pattern 440, and a connectionpart 16 connecting the conductive pattern 440 and the wiring part 15. Inthe illustrated example, the conductive pattern 440 is powered by apower source 7, such as a battery, through the wiring part 15 and theconnection part 16, so that the conductive pattern 440 generates heat bymeans of resistance heat. The heat generated by the conductive pattern440 is transmitted to the glass plates 411, 412 through the joint layers413, 414, so that the glass plates 411, 412 are warmed up. Thus, duedrops on the glass plates 411, 412 can be removed so that the glassplates 411, 412 can be defogged. When there is snow or ice on the glassplates 411, 412, the snow or ice can be unfrozen. Thus, an excellentfiled of view of a passenger can be ensured.

In order to manufacture the heating plate 410, as shown in FIG. 73, thecurved glass plate 411, the first joint layer 413, the conductivepattern sheet 420, the second joint layer 414 and the curved glass plate412 are superposed in this order, and heated/pressurized, so that thecurved glass plate 411, the conductive pattern sheet 420 and the curvedglass plates 412 are joined by the joint layers 413, 414.

The respective layers of the heating plate 410 are described below.

The glass plate 411, 412 is firstly described. Particularly when used asa front window, the glass plate 411, 412 preferably has a high visiblelight transmittance in order not to hinder a field of view of apassenger. A material of such a glass plate 411, 412 may be soda limeglass, blue plate glass and so on, for example. The glass plate 411, 412preferably has a transmittance of 90% or more in a visible light area.The visible light transmittance of the glass plate 411, 412 is specifiedas follows. Transmittance of light with measurement wavelength range offrom 380 nm to 780 nm is measured by using a spectrophotometer(manufactured by Shimadzu Corporation, “UV-3100PC”, compliant with JIS K0115). The visible light transmittance is an average value of thetransmittances at the respective wavelengths. The visible lighttransmittance may be lowered by partially or totally coloring the glassplate 411, 412, for example. In this case, direct sunlight can beshielded and an inside of the automobile is less visible from outside.

In addition, the glass plate 411, 412 preferably has a thickness of notless than 1 mm and not more than 5 mm. With such a thickness, the glassplate 411, 412 excellent in strength and optical properties can beobtained.

Next, the joint layers 413, 414 are described. The first joint layerr413 is disposed between the first glass plate 411 and the conductivepattern sheet 420 to join the first glass plate 411 and the conductivepattern sheet 420 to each other. In more detail, in this example, asshown in FIGS. 72 and 73, the first joint layer 413 is disposed betweenthe first glass plate 411 and the conductive pattern 440 of theconductive pattern sheet 420 to be directly in contact with the firstglass plate 411 and the thin conductive wires 441, so as to join theconductive pattern 440 to the first glass plate 411 through the thinconductive wires 441 with which the first joint layer 413 is in contact.Strictly speaking, the first joint layer 413 is directly in contact withthe first glass plate 411, the thin conductive wires 441 and a surface431 a of the substrate 430, so as to join the conductive pattern 440 tothe first glass plate 411 through the thin conductive wires 441 and thesurface 431 a with which the first joint layer 413 is in contact.

In addition, the second joint layer 414 is disposed between the secondglass plate 412 and the conductive pattern sheet 420 to join the secondglass plate 412 and the conductive sheet 420 to each other. In moredetail, in this example, the second joint layer 414 is disposed betweenthe second glass plate 412 and the substrate 430 of the conductivepattern sheet 420 to be directly in contact with the second glass plate412 and the substrate 430, so as to join the substrate 430 and thesecond glass plate 412.

As such a joint layer 413, 414, a layer made of a material havingvarious adhesion properties or gluing (pressure sensitive adhesive)properties can be employed. In addition, the joint layer 413, 414preferably has a high visible light transmittance. A typical joint layermay be a layer made of polyvinyl butyral (PVB), for example. The jointlayer 413, 414 preferably has a thickness of not less than 0.15 mm andnot more than 1 mm.

Not limited to the illustrated example, the heating plate 410 may beprovided with another function layer for exerting a specific function.In addition, one function layer may exert two or more functions.Alternatively, for example, a function may be given to at least one ofthe glass plate 411, 412 of the heating plate 410, the joint layer 413,414 thereof, and the substrate 430 of the conductive pattern sheet 420thereof, which is described later. The function that can be given toheating plate 410 may be an antireflection (AR) function, a hard coat(HC) function having an abrasion resistance, an infrared ray shield(reflection) function, an ultraviolet ray shield (reflection) function,a polarizing function, an antifouling function and so on, for example.

Next, the conductive pattern sheet 420 is described. As shown in FIGS.71 and 72, the conductive pattern sheet 420 in this embodiment includesa sheet-like substrate 430 having a pair of opposed surfaces 431 a, 431b, the conductive pattern 440 disposed on the surface 431 a of the pairof opposed surfaces 431 a, 431 b of the substrate 430, the wiring part15 for powering the conductive pattern 440, and the connection part 16connecting the conductive pattern 440 and the wiring part 15. Theconductive pattern sheet 420 may have a planar dimension substantiallythe same as that of the glass plate 411, 412 so as to be placed all overthe heating plate 410. Alternatively, the conductive pattern sheet 420may be placed over only a part of the heating plate 410, such as a partin front of a driver's seat.

The substrate 430 functions as a substrate that supports the conductivepattern 440. The substrate 430 is an electrically insulating substratethat transmits light of a wavelength (380 nm to 780 nm) of a visiblelight wavelength band, which is generally recognized as transparent. Thesubstrate 430 contains a thermoplastic resin.

A thermoplastic resin contained as a main component in the substrate 430may be any thermoplastic resin as long as it transmits visible light.The thermoplastic resin may be an acryl resin made of, e.g., polymethylmethacrylate, a polyolefin resin made of e.g., polypropylene, apolyester resin made of, e.g., polyethylene terephthalate orpolyethylene naphthalate, a cellulose-based resin made of, e.g.,triacetyl cellulose (cellulose triacetate), polyvinyl chloride,polystyrene, a polycarbonate resin, an AS resin and so on, for example.In particular, an acryl resin and polyethylene terephthalate arepreferred because of their excellent optical properties and moldability.

In addition, in consideration of light transmittance, suitable supportproperty of the conductive pattern 440, the substrate 430 preferably hasa thickness of not less than 0.02 mm and not more than 0.20 mm.

FIG. 74 is a plan view showing an example of an arrangement pattern ofthe conductive pattern 440. The conductive pattern 440 is powered by thepower source 7, such as a battery, through the wiring part 15 and theconnection part 16, so as to generate heat by means of resistance heat.The heat is transmitted to the glass plates 411, 412 through the jointlayers 413, 414, so that the glass plates 411, 412 are warmed up.

The conductive pattern 440 shown in FIG. 74 is a member including thethin conductive wires 441 that are arranged in a mesh pattern defining anumber of openings 443. The conductive pattern 440 is a member that isalso referred to as conductive mesh. The conductive pattern 440 includesthe plurality of connection conductive wires 441 that extend between twobranch points 442 to define the openings 443. Namely, the conductivepattern 440 is an aggregation of a number of the thin conductive wires441 each forming the branch points 442 at both ends thereof.Particularly in the illustrated example, the three thin conductive wires441 are connected at equal angles at each branch point 442, so thatthere are defined a number of the openings 443 of the same honeycombshape (hexagonal shape) each of which is surrounded by the sixconnection elements 441.

In the illustrated example, the conductive pattern 440 includes the thinconductive wires 441 that are arranged in a mesh pattern in which theopenings 443 of the same honeycomb shape are regularly defined. However,not limited to the mesh pattern, the conductive pattern 440 may have thethin conductive wires 441 that are arranged in various mesh patternssuch as in a mesh pattern (grid pattern) in which the openings 443 ofthe same shape such as a triangular shape or a rectangular shape areregularly defined, a mesh pattern in which the openings 443 of differentshapes are regularly defined, a mesh pattern in which the openings 443of different shapes are irregularly defined, such as a Voronoi meshpattern, and so on. In addition, the conductive pattern 440 may have aline and space pattern formed by a plurality of the thin conductivewires 441 that are arranged in one direction.

The conductive pattern 440 may be made of one or more of gold, silver,copper, platinum, aluminum, chrome, molybdenum, nickel, titanium,palladium, indium, tungsten and an alloy thereof. The conductive pattern440 is formed of a metal film in which the thin conductive wires 441 arepatterned by etching. The conductive pattern 440 may include a thinwire, i.e., a connection wire connecting the adjacent thin conductivewires 441.

FIG. 75 is a sectional view showing the A-A line of FIG. 74, showing asectional shape of the thin conductive wire 441. FIG. 75 shows thesectional shape of the thin conductive wire 441 in a directionperpendicular to an extension direction of the thin conductive wire 441(referred to simply as “sectional shape” or “section” herebelow). Thethin conductive wires 441 constituting the conductive pattern 440 areformed on the substrate 430 (surface 431 a). In the illustrated example,the thin conductive wire 441 includes a surface 441 a on the side of thesubstrate 430, a surface 441 b on the side opposed to the substrate 430,and side surfaces 441 c, 441 d. In the illustrated example, the surface441 a on the side of the substrate 430 and the surface 441 b on the sideopposed to the substrate 430 are in parallel. The side surface 441 cforms a tapered surface that is tapered to come close to the sidesurface 441 d as a certain point in the side surface 441 c moves awayfrom the substrate 430 along a normal direction of the sheet plane ofthe conductive pattern sheet 420. The side surface 441 d also forms atapered surface that is tapered to come close to the side surface 441 cas a certain point in the side surface 441 d moves away from thesubstrate 430 along the normal direction of the sheet plane of theconductive pattern sheet 420. Namely, the thin conductive wire 441 hassubstantially a trapezoidal section in general, in the sectional viewperpendicular to the extension direction thereof.

More specifically, the thin conductive wire 441 is formed such that aline width thereof narrows along the normal direction to the sheet planeof the substrate 430, i.e., the line width narrows as a certain point inthe thin conductive wire 441 moves away outward from the surface 431 a.In addition, as shown in FIG. 72, when the conductive pattern sheet 420is incorporated in the heating plate 410, the thin conductive wire 441is formed such that its line width narrows as a certain point in thethin conductive wire 441 comes close to the first glass plate 411located on the side of the first joint layer 413 in contact with thethin conductive wire 441 (The thin conductive wire 441 is formed suchthat its line gradually becomes smaller towards the first glass plate411 located on the side of the first joint layer 413 in contact with thethin conductive wire 441).

FIG. 76A and FIG. 76B are enlarged views of the sectional shape of thethin conductive wire 441 shown in FIG. 75. FIG. 76A shows, in thetrapezoidal sectional shape of the thin conductive wire 441, an angle αwhich is defined by a line segment forming a sidewall of the thinconductive wire 441, which extends from an end of a lower base (surface441 a) to an end of an upper base (surface 441 b), with respect to adirection extending along the lower base. The angle α is preferably anangle in a range between not less than 40 degrees and not more than 85degrees. When the angle α is less than 40 degrees, suitable heatgeneration is difficult to be obtained unless a line width of the thinconductive wire 441 is increased. As a result, the thin conductive wire441 having a larger width may deteriorate visibility of the heatingplate 410. Thus, the angle α is preferably not less than 40 degrees.

FIG. 76A shows an example in which the sectional shape of the thinconductive wire 441 is a neat trapezoidal shape. However, as shown inFIG. 76B, there is a possibility that the side surfaces 441 c, 441 d areformed of curved lines because of manufacturing conditions and so on. Inthe present invention, such a shape is included in a concept oftrapezoidal shape. Also in this case, as shown in FIG. 76B, the angle αis specified as an angle defined by the line segment which extends fromthe end of the lower base (surface 441 a) to the end of the upper base(surface 441 b), with respect to the direction extending along the lowerbase. This angle α is also preferably not less than 40 degrees and notmore than 85 degrees. In this embodiment, the sectional shape of thethin conductive wire 441 is trapezoidal. However, as long as the thinconductive wire 441 is formed such that its line width narrows as acertain point in the thin conductive wire 441 comes close to the firstglass plate 411, the thin conductive wire 441 may have a tier-likeshape, for example.

In a case where the thin conductive wire 441 is formed such that itsline width narrows as a certain point in the thin conductive wire 441comes close to the first glass plate 411 located on the side of thefirst joint layer 413 in contact with the thin conductive wire 441, whenthe glass plates 411, 412, the joint layers 413, 414 and the conductivepattern sheet 420 are laminated, the joint layer 421 can easily get intoa root side of the thin conductive wire 441. As a result it can berestrained that bubbles remain around the sidewalls (surfaces 441 c, 442d) of the thin conductive wire 441.

In FIG. 75, W_(max) represents a line width of the thin conductive wire441 on the root along the sheet plane of the substrate 430, showing aline width of a part having a largest width of the thin conductive wire441 (referred to as “maximum width” herebelow). In this embodiment, themaximum width W_(max) of the thin conductive wire 441 is not less than 1μm and not more than 20 μm. The maximum width W_(max) is preferably notless than 2 μm and not more than 20 μm, and more preferably not lessthan 2 μm and not more than 15 μm. Thus, the conductive pattern 440 isseen transparent in general, and has an excellent see-through property.In addition, a height (thickness) H of the thin conductive wire 441,i.e., the height (thickness) H along the normal direction to the sheetplane of the substrate 430 is preferably not less than 1 μm and not morethan 20 μm, and more preferably not less than 1 μm and not more than 12μm. Since the thin conductive wire 441 having such a height dimension,in addition to the line width W_(max), is sufficiently thin, theconductive pattern 440 can be effectively made invisible.

In FIG. 75, the symbol P represents a pitch between the adjacentopenings 443 (distance between centers of the adjacent openings 443) inthe honeycomb pattern of the conductive pattern 440 when it has ahoneycomb pattern. The pitch P is preferably not less than 0.3 mm andnot more than 2 mm. The pitch P may be not less than 0.3 mm and not morethan 7.0 mm. When the conductive pattern 440 has a grid pattern, a pitchbetween adjacent rectangular openings in the grid pattern is preferablynot less than 0.3 mm and not more than 2 mm. Also in this case, thepitch may be not less than 0.3 mm and not more than 7.0 mm. In addition,when the conductive pattern 440 has a line and space pattern, a pitch,which is a distance between the adjacent thin conductive wires 441, ispreferably not less than 0.3 mm and not more than 2 mm. Also in thiscase, the pitch P may be not less than 0.3 mm and not more than 7.0 mm.

In addition, in the illustrated example, the thin conductive wire 441includes a first dark color layer 446 disposed on the substrate 430, aconductive metal layer 445 disposed on the first dark color layer 446,and a second dark color layer 447 disposed on the conductive metal layer445. In other words, the surface of the conductive metal layer 445 onthe side of the substrate 430 is covered with the first dark color layer446, and the surface of the conductive metal layer 445 on the sideopposed to the substrate 430 and both side surfaces thereof are coveredwith the second dark color layer 447.

The conductive metal layer 445 made of a metal material has relatively ahigh reflectance. When light is reflected on the conductive metal layer445 forming the conductive metal wires 441 of the conductive pattern440, the reflected light may be visible, which hinders a field of viewof a passenger. In addition, when the conductive metal layer 445 isvisible from outside, design is sometimes impaired. Thus, the dark colorlayers 446, 447 are disposed at least a part of the surface of theconductive metal layer 445. The dark color layers 446, 447 are layerhaving a visible light reflectance that is lower than that of theconductive metal layer 445, and are black-colored dark color layers, forexample. Due to the dark color layers 446, 447, the conductive metallayer 445 becomes less visible, whereby an excellent field of view of apassenger can be ensured. In addition, impairment of design when seenfrom outside can be prevented. However, such dark color layers 446, 447may be omitted.

Next, an example of a manufacturing method of the heating plate 410 isdescribed with reference to FIGS. 77 to 86. FIGS. 77 to 86 are sectionalviews showing the example of the manufacturing method of the heatingplate 410 in sequence. In particular, FIGS. 77 to 85 are views forexplaining manufacture of the conductive pattern sheet 420 in detail.FIG. 86 shows that, after the conductive pattern sheet 420 ismanufactured, the conductive pattern sheet 420 is sandwiched between theglass plates 411, 412 so that the heating plate 410 is manufactured.

In order to manufacture the conductive pattern sheet 420, as shown inFIG. 77, there is firstly prepared a metal foil 450 having a pair ofopposed surfaces 450 a, 450 b. The metal foil 450 will form theconductive metal layer 445 of the thin conductive wire 441. The metalfoil 450 may be a foil made of gold, silver, copper, platinum, aluminum,chrome, molybdenum, nickel, titanium, palladium, indium, tungsten and analloy thereof, for example. A thickness of the metal foil 450 may be notless than 1 μm and not more than 60 μm.

Then, as shown in FIG. 78, in the illustrated example, a dark color film460, which will form the first dark color layer 446 of the thinconductive wire 441, is formed on the surface 450 b of the metal foil450. In this example, the dark color film 460 is made of chrome oxide.When the dark color film 460 to be formed on the metal foil 450 is madeof chrome oxide, the dark color film 460 may be deposited by aspattering method or a vacuum vapor deposition method, for example, ormay be formed by a treatment with a solution of sodium chlorite, sodiumhydroxide and trisodium phosphate. In addition, for example, the darkcolor film 460 may be formed by subjecting a part of a materialconstituting the metal foil 450 to a darkening treatment (blackeningtreatment), and the first dark color film 460 made of metallic oxide ormetallic sulfide can be formed from the part constituting the metal foil450. In addition, the dark color film 460 may be made of copper nitride,copper oxide, nickel nitride and so on.

Then, as shown in FIG. 79, the substrate 430 is prepared. The substrate430 and the metal foil 450 are located such that the surface 431 a ofthe substrate 430 and the surface 450 b of the metal foil 450 on whichthe dark color film 460 was formed face each other. Thereafter, as shownin FIG. 80, the metal foil 450 is laminated on the surface 431 a of thesubstrate 430 through an adhesive layer. The substrate 430 may have athickness of not less than 0.02 mm and not more than 0.20 mm, and may bemade of polyethylene terephthalate, polyethylene naphthalate,polycarbonate, polystyrene, cyclic polyolefin and so on.

Then, as shown in FIG. 81, the resist layer 448 is disposed on the metalfoil 450. The resist layer 448 is a resin layer having aphotosensitivity to light of a predetermined wavelength range, such asultraviolet light. The resin layer may be formed by adhering a resinfilm, or may be formed by applying a flowable resin. A concretephotosensitive property of the resist layer 448 is not specificallylimited. For example, a photo-curing type photosensitive material or aphoto-dissolving photosensitive material may be used as the resist layer448.

Thereafter, as shown in FIG. 82, the resist layer 448 is patterned toform (laminate) a resist pattern 449. Various known methods may be usedas the method of patterning the resist pattern 449. In this example, aresin layer having a photosensitivity to light of a predeterminedwavelength range, such as ultraviolet light, is used as the resist layer448, and a known photolithographic technique is used for patterning theresist layer 448. Firstly, a mask which opens a part to be patterned ora mask which shields a part to be patterned is placed on the resistlayer 448, and the resist layer 448 is irradiated with ultraviolet lightthrough the mask. Thereafter, the part shielded by the mask from theultraviolet light or the part irradiated with the ultraviolet light isdeveloped and removed by means of solution such as a water. Thereafter,the remaining resist layer 448 is subjected to a curing process such asa heating process or a chrome film curing process and so on, and is thenbaked at a predetermined temperature. Thus, the patterned resist pattern449 can be formed.

Then, as shown in FIG. 83, the metal foil 450 including the dark colorfilm 460 is etched with the resist pattern 449 serving as a mask. Due tothis etching process, the metal foil 450 including the dark color film460 is patterned substantially similar to the resist pattern 449. As aresult, the conductive metal layer 445, which will form a part of thethin conductive wire 441, is formed from the patterned metal foil 450.In addition, the first dark color layer 446, which will form a part ofthe thin conductive wire 441, is formed from the patterned dark colorfilm 460. The conductive metal layer 445 is formed such that its linewidth narrows along the normal direction to the sheet plane of thesubstrate 430, i.e., the line width narrows as a certain point in thethin conductive wire 441 moves away outward from the surface 431 a. Theetching method is not particularly limited, and a known method may beemployed. The known method may be a wet etching method using etchant, aplasma etching method and so on.

In this embodiment, in order that the line width of the conductive metallayer 445 has a desired shape, i.e., the line width narrows as a certainpoint in the conductive metal wire 445 moves away from the surface 431a, a predetermined operation is carried out. One example of thepredetermined operation for forming the desired shape is an operationthat lowers a contact between the resist pattern 449 and the metal foil450. A concrete method of lowering the contact is as follows. In thebaking step at a predetermined temperature which is performed after theprocess for curing the remaining resist layer 448 after being developedin the step of forming the resist pattern 449, the baking is performedat a temperature less than 100 degrees, e.g., not less than 80 degreesand not more than 95 degrees, in order that the resist pattern 449 iscompletely dried. In addition, another example of the predeterminedoperation for forming the desired shape is as follows. When the metalfoil 450 including the dark color film 460 is etched with the resistpattern 449 serving as a mask, wet etching is employed. In this case, aconcentration of an etchant used in the wet etching is made to begreater than a predetermined concentration, or a temperature of theetchant is made to be higher than a predetermined temperature, or anetching period by the etchant is made shorter than a predeterminedperiod. A yet another example of the predetermined operation for formingthe desired shape is as follows. When an ultraviolet curing type resinis used in the resist layer 448, a UV intensity of the resin is lowered.

After the metal foil 450 including the dark color film 460 is etched asdescribed above, the resist pattern 449 is removed as shown in FIG. 84.

Then, as shown in FIG. 85, the second dark color layer 447 is formed onthe surface 441 a of the conductive metal layer 445 on the side opposedto the first dark color layer 446 and the side surfaces 441 c, 441 d.The second dark color layer 447 is formed by, e.g., subjecting a part ofa material constituting the conductive metal layer 445 to a darkeningtreatment (blackening treatment). Namely, in this case, the second darkcolor layer 447 made of metallic oxide or metallic sulfide can be formedfrom the part constituting the conductive metal layer 445.Alternatively, the second dark color layer 447 as a coating film made ofa dark color material or a plated layer made of nickel or chrome may bedisposed on the surface of the conductive metal layer 445. In addition,the surface of the conductive metal layer 445 may be roughened, and thesecond dark color layer 447 may be disposed thereon.

In this manner, the conductive pattern sheet 420 is manufactured.Thereafter, as shown in FIG. 86, the curved first glass plate 411, thefirst joint layer 413, the conductive pattern sheet 420, the secondjoint layer 414 and the curved second glass plate 412 are superposed inthis order, and heated and pressurized, so that the curved first glassplate 411, the conductive pattern sheet 420 and the curved second glassplate 412 are joined by the joint layers 413, 414. Therefore, theheating plate 420 is manufactured.

The aforementioned heating plate 410 in this embodiment includes thepair of glass plates 411, 412, and the conductive pattern 440 disposedbetween the pair of glass plates 411, 412. The conductive pattern 440has the thin conductive wires 441 that are arranged in a pattern. Inaddition, the heating plate 410 includes the first joint layer 413disposed between the first glass plate 411 of the pair of glass platesand the conductive pattern 440 to be directly in contact with the firstglass plate 411 and the thin conductive wires 441, so as to join theconductive pattern 440 to the first glass plate 411. The thin conductivewire 441 is formed such that its line width narrows as a certain pointin the thin conductive wire 441 comes close to the first glass plate 411located on the side of the first joint layer 413 with which the thinconductive wire 441 is in contact.

According to such a heating plate 410, when the glass plates 411, 412,the joint layers 413, 414 and the conductive pattern sheet 420 arelaminated during the manufacturing process, the joint layer 413 caneasily get into the root side of the thin conductive wire 441,particularly upon heating. As a result it can be restrained that bubblesremain around the sidewalls (surfaces 441 c, 442 d) of the thinconductive wire 441. Thus, according to this embodiment, an appearancequality of the heating plate 410 can be improved, and glaring isrestrained from occurring in the heating plate 410.

The aforementioned embodiment can be variously modified. Modificationexamples are described with reference suitably to the drawings. In thebelow description and the drawings for the description, a component thatcan be similarly made as that of the above embodiment is shown by thesame symbol as a component corresponding to the above embodiment, andoverlapped description is omitted.

In a modification example shown in FIG. 87, the conductive pattern 440is disposed on a surface of the first glass plate 411 facing the secondglass plate 412, through a holding layer not shown. The substrate 430 asdescribed in the above embodiment is not provided. The holding layer hasa thickness of about 1 μm to 100 μm. The holding layer joins theconductive pattern 440 to the first glass plate 411, by a peeling layer(illustration omitted) formed on a surface facing the glass plate 411.On the other hand, a third joint layer 423 is disposed between theconductive pattern 440 and the second glass plate 412. The third jointlayer 423 is directly in contact with the second glass plate 412 and thethin conductive wires 441, so as to join the conductive pattern 440 tothe second glass plate 412 through the thin conductive wires 441 withwhich the third joint layer 423 is in contact. The thin conductive wire441 is formed such that a line width thereof narrows as a certain pointin the thin conductive wire 441 comes close to the second glass plate412 located on the side of the third joint layer 423. Also in thismodification example, the same effect as that of the above embodimentcan be obtained. In this example, when the conductive pattern 440 isformed by patterning, there exists a substrate that supports theconductive pattern 440. However, this substrate is peeled when theconductive pattern 440 is joined to the first glass plate 411. Thus, theabove-described holding layer is exposed. The peeling layer formed onthe holding layer may be, for example, a peeling layer of an interfacepeeling type, a peeling layer of an interlayer peeling type, a peelinglayer of a cohesion peeling type and so on.

Next, in a modification example shown in FIG. 88, the conductive pattern440 is disposed on the respective surfaces 431 a, 431 b of the substrate430 in the conductive pattern sheet 420. The first joint layer 413 isdisposed between the first glass 411 and the conductive pattern 440provided on the surface 431 a. The first joint layer 413 is directly incontact with the first glass plate 411 and the thin conductive wires 441of the conductive pattern 440 provided on the surface 431 a, so as tojoin the conductive pattern 440 to the first glass plate 411 through thethin conductive wire 441 with which the first joint layer 413 is incontact. The thin conductive wire 441 is formed such that a line widththereof narrows as a certain point in the thin conductive wire 441 comesclose to the first glass plate 411 located on the side of the firstjoint layer 413 in contact with the thin conductive wire 441.

On the other hand, the second joint layer 414 is disposed between thesecond glass plate 412 and the conductive pattern 440 provided on thesurface 431 b. The second joint layer 414 is directly in contact withthe second glass plate 412 and the thin conductive wire 441 of theconductive pattern 440 provided on the surface 431 b, so as to join theconductive pattern 440 to the second glass plate 412 through the thinconductive wire 441 with which the second joint layer 412 is in contact.The thin conductive wire 441 is formed such that a line width thereofnarrows as a certain point in the thin conductive wire 441 comes closeto the second glass plate 412 located on the side of the second jointlayer 414 in contact with the thin conductive wire 441. Also in thismodification example, the same effect as that of the above embodimentcan be obtained.

The aforementioned embodiment and the modification examples can be morevariously modified.

For example, in the example shown in FIG. 75, the second dark colorlayer 447 is formed on the surface 441 a of the conductive metal layer445 on the side opposed to the first dark color layer 446 and the sidesurfaces 241 c, 241 d. However, not limited thereto, the second darkcolor layer 247 may be formed only on the surface 441 a of theconductive metal layer 445 on the side opposed to the first dark colorlayer 446, or only on the side surfaces 441 c, 441 d of the conductivemetal layer 445.

When the second dark color layer 447 is formed only on the surface 441 aof the conductive metal layer 245 on the side opposed to the first darkcolor layer 446, after the step shown in FIG. 80, for example, thesecond dark color layer 447 and the resist pattern 449 are disposed inthis order on the metal foil 450. Thereafter, the second dark colorlayer 447, the conductive metal layer 445 and the first dark color layer446 are etched with the resist pattern 449 serving as a mask.

Alternatively, when the second dark color layer 447 is formed only onthe side surfaces 441 c, 441 d of the conductive metal layer 445, afterthe step shown in FIG. 83, for example, the second dark color layer 447is formed without removing the resist pattern 449. After that, theresist pattern 449 is removed.

The heating plate 410 may be used in a rear window, a side window and asun roof of the automobile 1. In addition, the heating plate 410 may beused in a window of a vehicle other than an automobile, such as arailway, an aircraft, a vessel, a space vessel and so on.

Further, in addition to a vehicle, the heating plate 410 may be used ina part by which an inside and an outside is partitioned, such as awindow of a building, a store and a house.

Although some modification examples of the above third embodiment aredescribed, the modification examples can be naturally combined with oneanother for application.

The present invention is described in more detail herebelow by using anexample. However, the present invention is not limited to the example.

Example

The heating plate 410 in Example was manufactured as follows. As thesubstrate 430, there was firstly prepared a PET (polyethyleneterephthalate) film (manufactured by TOYOBO Co., Ltd A4300) having athickness of 100 μm, a width of 82 cm and a length of 100 m. A two-packmixture type urethane ester-based adhesive was applied to the substrate430 by a gravure coater, such that a thickness of the cured adhesivebecame 7 μm. Then, an electrolytic copper foil having a thickness of 10μm, a width of 81 cm and a length of 80 m was laminated as the metalfoil 450 on the substrate 430 through an adhesive. The electrolyticcopper foil and the substrate 430 were maintained for 4 days in anenvironment of 50° C., so that the electrolytic copper foil was securedon the substrate 430.

Thereafter, casein was applied to the electrolytic copper foil (metalfoil 450) and dried so as to laminate the resist layer 48 as aphotosensitive resin layer. Then, in a plurality of ranges specified by100 cm×80 cm in the resist layer 48, a mesh-like pattern of 3.0 mm inpitch and 7 μm in line width was exposed with a photomask having apattern formed thereon. In this exposure process, ultraviolet contactexposure was intermittently carried out. After the exposure process, apart where the resist pattern 449 was not formed was developed by waterand removed. The remaining resist layer 48 was heated at 80° C. for 2minutes and was baked at a temperature of 85 degrees. Thus, the resistpattern 449 was formed. The resist pattern 449 was formed in a mesh-likepattern of 3.0 mm in pitch and 7 μm in line width.

Then, a ferric chloride solution (Baume degree of 42, temperature of 30degrees) was sprayed to the metal foil 450 from the resist pattern 449,with the resist pattern 449 serving as a mask, so as to etch the metalfoil 450. After cleaning with water, the resist is peeled by using analkali solution. After the resist was peeled, cleaning and drying werecarried out. Then, there was obtained a laminate including a pluralityof the conductive pattern sheets 420 including the substrate 430 made ofPET/the adhesive layer/the conductive pattern 440 made of copper(conductive mesh). The conductive pattern 440 in the conductive patternsheet 420 was made as a range of 100 cm×80 cm wherein the thinconductive wires 441 were arranged in a mesh-like pattern of 3.0 mm inpitch and 7 μm in line width. The thin conductive wire 441 was formedinto a trapezoidal shape in a section in a direction perpendicular tothe extension direction of the thin conductive wire. In the trapezoidalsection of the thin conductive wire 441, an angle α that was defined bya line segment which extends from an end of a lower base (surface 441 a)to an end of an upper base (surface 441 b), with respect to a directionextending along the lower base, i.e., a basic angle was 75 degrees.

Then, the conductive pattern sheet 420 of 100 cm×80 cm was cut from thethus obtained laminate. The conductive pattern sheet 420 was sandwichedbetween the joint layers 413, 414 formed of PVB adhesive sheets havingthe same size as that of the conductive pattern sheet 420. Then, theyare further sandwiched between the glass plates 411, 412 of 100 cm×80cm, and were heated/pressurized (vacuum laminated). Then, the heatingplate 410 according to Example was obtained.

Upon inspection of the heating plate 410 according to Example with eyes,no bubble was found. In addition, when a point light source distant from3 m was observed via the heating plate 410, there was no fine glaringcaused by bubbles.

Comparative Example

A heating plate in Comparative Example was manufactured by using thesame materials and the same steps as those of Example, excluding that abaking temperature for forming the resist pattern was 100 degrees. Inthe heating plate in Comparative Example, the thin conductive wire had arectangular sectional shape in a direction perpendicular to theextension direction of the thin conductive wire. The basic angle wasabout 90 degrees. Upon inspection of the heating plate in ComparativeExample with eyes, some bubbles were found. In addition, when a pointlight source distant from 3 m was observed via the heating plate, therewas fine glaring caused by bubbles.

1. A heating plate that generates heat upon application of voltagethereto, the heating plate comprising: a pair of glass plates; aconductive pattern disposed between the pair of glass plates anddefining a plurality of opening areas; and a joint layer disposedbetween the conductive pattern and at least one of the pair of glassplates; the conductive pattern includes a plurality of connectionelements that extend between two branch points to define the openingareas; and a rate of the connection elements, which are straight linesegments connecting the two branch points, relative to the plurality ofconnection elements, is less than 20%.
 2. The heating plate according toclaim 1, wherein the conductive pattern has the opening areas that haverandom shapes and are arranged at random pitches.
 3. The heating plateaccording to claim 1, wherein the conductive pattern is formed bypatterning a conductive layer by etching.
 4. The heating plate accordingto claim 1, wherein an average distance between centers of gravity ofthe two adjacent opening areas is not less than 70 μm.
 5. The heatingplate according to claim 1, wherein a thickness of the conductivepattern is not less than 2 μm.
 6. The heating plate according to claim1, wherein an average of ratio (L₁/L₂) of a length L₁ of each openingarea along a first direction, relative to a length L₂ of the openingarea along a second direction perpendicular to the first direction, isnot less than 1.3 and not more than 1.8.
 7. A conductive pattern sheetused in a heating plate that generates heat upon application of voltagethereto, the conductive pattern sheet comprising: a substrate; and aconductive pattern disposed on the substrate and defining a plurality ofopening areas; wherein: the conductive pattern includes a plurality ofconnection elements that extend between two branch points to define theopening areas; and a rate of the connection elements, which are straightline segments connecting the two branch points, relative to theplurality of connection elements, is less than 20%.
 8. A vehiclecomprising the heating plate according to claim
 1. 9. A heating platethat generates heat upon application of voltage thereto, the heatingplate comprising: a pair of glass plates; a conductive pattern disposedbetween the pair of glass plates and including a thin conductive wire;and a joint layer disposed between the conductive pattern and at leastone of the pair of glass plates; wherein: the thin conductive wire ofthe conductive pattern has a first surface facing one of the pair ofglass plates, and a second surface facing the other of the pair of glassplate; and when a width of the first surface of the thin conductive wireis represented as W_(2a) (μm), a width of the second surface of the thinconductive wire is represented as W_(2b) (μm), and a cross-sectionalarea of the thin conductive wire is represented as S_(2a) (μm²), thefollowing relationships represented (a) and (b) are satisfied.0<IW _(2a) −W _(2b) I≦10  (a)S _(2a)≧10  (b)
 10. The heating plate according to claim 9, wherein theconductive pattern is formed by patterning a conductive layer byetching.
 11. The heating plate according to claim 9, wherein theconductive pattern includes a pattern defining a plurality of openingareas; and the conductive pattern includes a plurality of connectionelements that extend between two branch points to define the openingareas.
 12. The heating plate according to claim 11, wherein an averageof the number of the connection elements extending from one branch pointis more than 3.0 and less than 4.0.
 13. The heating plate according toclaim 11, wherein; the conductive pattern includes opening areassurrounded by four, five, six and seven connection elements,respectively; and among the opening areas included in the conductivepattern, the number of opening areas surrounded by six connectionelements is predominant.
 14. The heating plate according to claim 11,wherein at least some of the plurality of connection elements have acurved shape or a polygonal line shape, when viewed in a normaldirection of a plate plane of the heating plate.
 15. The heating plateaccording to claim 9, wherein: the conductive pattern includes aplurality of the thin conductive wires; and the plurality of thinconductive wires are arranged apart from one another in a direction notin parallel with a direction in which the thin conductive wires extend.16. The heating plate according to claim 15, wherein the thin conductivewires adjacent in the non-parallel direction are connected by aconnection wire.
 17. A conductive pattern sheet used in a heating platethat generates heat upon application of voltage thereto, the conductivepattern sheet comprising: a substrate; and a conductive pattern disposedon the substrate and including a thin conductive wire; wherein: the thinconductive wire of the conductive pattern has a proximal surface forminga surface on the side of the substrate, and a distal surface facing theproximal surface; when a width of the distal surface of the thinconductive wire is represented as W_(2c) (μm), a width W_(2d) of theproximal surface of the thin conductive wire is represented as W_(2d)(μm), and a cross-sectional area of the thin conductive wire isrepresented as S_(2b) (μm²), the following relationships represented (c)and (d) are satisfied.0<IW _(2c) −W _(2d) I≦10  (c)S _(2b)≧10  (d)
 18. A vehicle comprising the heating plate according toclaim
 9. 19. A heating plate comprising: a pair of glass plates; and aconductive pattern disposed between the pair of glass plates; wherein:the conductive pattern includes a plurality of thin conductive wiresthat are formed of a patterned copper film and are arranged in onedirection, each thin conductive wire extending in the other directionnot in parallel with the one direction apart from another thinconductive wire adjacent in the one direction; a line width of the thinconductive wire is not less than 1 μm and not more than 20 μm; and apitch between the adjacent thin conductive wires is not less than 0.3 mmand not more than 2 mm.
 20. A heating plate comprising: a pair of glassplates; and a conductive pattern disposed between the pair of glassplates; wherein: the conductive pattern includes a plurality of thinconductive wires that are formed of a patterned copper film and arearranged in a line and space pattern; a line width of the thinconductive wire is not less than 1 μm and not more than 20 μm; and apitch between the adjacent thin conductive wires is not less than 0.3 mmand not more than 2 mm.
 21. The heating plate according to claim 19,wherein each thin conductive wire extends in a pattern of a polygonalline shape or in a pattern of a corrugated shape.
 22. The heating plateaccording to claim 19, wherein the copper film is an electrolytic copperfoil.
 23. A manufacturing method of a heating plate including a pair ofglass plates and a conductive pattern disposed between the pair of glassplates, the manufacturing method comprising: laminating a copper film ona substrate; and forming the conductive pattern including a plurality ofthin conductive wires formed by patterning the copper film; wherein: theplurality of thin conductive wires are arranged in one direction; eachthin conductive wire extends in the other direction not in parallel withthe one direction apart from another thin conductive wire adjacent inthe one direction; and a line width of the thin conductive wire is notless than 1 μm and not more than 20 μm, and a pitch between the adjacentthin conductive wires is not less than 0.3 mm and not more than 2 mm.24. A manufacturing method of a heating plate including a pair of glassplates and a conductive pattern disposed between the pair of glassplates, the manufacturing method comprising: laminating a copper film onthe substrate; and forming the conductive pattern including a pluralityof thin conductive wires formed by patterning the copper film; wherein:the plurality of thin conductive wires are arranged in a line and spacepattern; and a line width of the thin conductive wire is not less than 1μm and not more than 20 μm, and a pitch between the adjacent thinconductive wires is not less than 0.3 mm and not more than 2 mm.
 25. Themanufacturing method of a heating plate according to claim 23, whereinthe copper film is an electrolytic copper foil.
 26. A heating platecomprising: a pair of glass plates; and a conductive pattern disposedbetween the pair of glass plates; wherein: the conductive patternincludes thin conductive wires formed of a patterned copper film andarranged in a mesh pattern; and a line width of the thin conductive wireis not less than 1 μm and not more than 20 μm.
 27. The heating plateaccording to claim 26, wherein the thin conductive wires are arranged ina honeycomb pattern.
 28. The heating plate according to claim 27,wherein a pitch of adjacent hexagonal openings in the honeycomb patternis not less than 0.3 mm and not more than 7.0 mm.
 29. The heating plateaccording to claim 26, wherein the thin conductive wires are arranged ina grid pattern.
 30. The heating plate according to claim 29, wherein apitch of adjacent rectangular openings in the grid pattern is not lessthan 0.3 mm and not more than 7.0 mm.
 31. The heating plate according toclaim 26, wherein the copper film is an electrolytic copper foil.
 32. Aconductive pattern sheet used in a heating plate that generates heatupon application of voltage thereto, the conductive pattern sheetcomprising: a substrate; and a conductive pattern disposed on thesubstrate; wherein: the conductive pattern includes thin conductivewires formed of a patterned copper film and arranged in a mesh pattern;and a line width of the thin conductive wire is not less than 1 μm andnot more than 20 μm.
 33. A manufacturing method of a heating plateincluding a pair of glass plates and a conductive pattern disposedbetween the pair of glass plates, the manufacturing method comprising:laminating a copper film on a substrate; and forming the conductivepattern including thin conductive wires formed by patterning the copperfilm; wherein: the thin conductive wires are arranged in a mesh pattern;and a line width of the thin conductive wire is not less than 1 μm andnot more than 20 μm.
 34. The manufacturing method according to claim 33,wherein the copper film is an electrolytic copper foil.
 35. A heatingplate including a pair of glass plates and a conductive pattern disposedbetween the pair of glass plates, the conductive pattern including thinconductive wires arranged in a pattern, the heating plate comprising: ajoint layer disposed between at least one of the pair of glass platesand the conductive pattern, the joint layer being directly in contactwith the glass plate and the thin conductive wires so as to join theconductive pattern to the glass plate; wherein the thin conductive wireis formed such that a line width thereof narrows as a certain point inthe thin conductive wire comes close to the glass plates located on theside of the joint layer in contact with the thin conductive wires. 36.The heating plate according to claim 35, wherein the thin conductivewires are formed from a metal film that is patterned by etching.
 37. Theheating plate according to claim 35, wherein the thin conductive wire isformed to have a trapezoidal sectional shape in a directionperpendicular to an extension direction of the thin conductive wire. 38.The heating plate according to claim 37, wherein the trapezoidalsectional shape in the thin conductive wire has an angle which isdefined by a line segment extending from an end of a lower base to anend of an upper base, with respect to a direction extending along thelower base, the angle being not less than 40 degrees and not more than85 degrees.
 39. The heating plate according to claim 35, wherein thethin conductive wire has a dark color layer at a position facing a sideopposed to the glass plate located on the side of the joint layer incontact with the thin conductive wire.
 40. The heating plate accordingto claim 39, wherein the dark color layer is made of chrome oxide.
 41. Aconductive pattern sheet having a conductive pattern to be disposedbetween a pair of glass plates, comprising: a sheet-like substrateincluding a pair of opposed surfaces; wherein: the conductive pattern isprovided at least any of the pair of opposed surfaces of the substrate;the conductive pattern includes thin conductive wires arranged in apattern; and the thin conductive wire is formed such that a line widththereof narrows as a certain point in the thin conductive wire movesaway outward from the substrate along a normal direction to a sheetplane of the substrate.